Fermi Gamma-ray Space Telescope

NASA's Fermi Gamma-ray Space Telescope has completed its primary mission, and it will continue to explore the high-energy cosmos in unprecedented detail. These pages gather together media products associated with Fermi news releases starting before its 2008 launch, when it was known as GLAST.

Fermi detects gamma rays, the most powerful form of light, with energies thousands to billions of times greater than the visible spectrum.

The mission has discovered pulsars, proved that supernova remnants can accelerate particles to near the speed of light, monitored eruptions of black holes in distant galaxies, and found giant bubbles linked to the central black hole in our own galaxy.

For more information about the Fermi mission, visit its NASA webpage.

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Edited Videos

  • NASA's Fermi Links Cosmic Neutrino to Monster Black Hole
    2018.07.12
    For the first time ever, scientists using NASA’s Fermi Gamma-ray Space Telescope have found the source of a high-energy neutrino from outside our galaxy. This neutrino travelled 3.7 billion years at nearly light speed before being detected on Earth -- farther than any other neutrino we know the origin of. High-energy neutrinos are hard-to-catch particles that scientists think are created by the most powerful events in the cosmos, like galaxy mergers and material falling onto supermassive black holes. They travel a whisker shy of the speed of light and rarely interact with other matter, so they can travel unimpeded across billions of light-years. On Sept. 22, 2017, the IceCube Neutrino Observatory at the South Pole detected signs of a neutrino striking the Antarctic ice with an energy of about 300 trillion electron volts -- more than 45 times the energy achievable in the most powerful particle accelerator on Earth. This high energy strongly suggested that the neutrino had to be from beyond our solar system. Backtracking the path through IceCube indicated where in the sky the neutrino came from, and automated alerts notified astronomers around the globe to search this region for flares or outbursts that could be associated with the event. Data from Fermi’s Large Area Telescope revealed enhanced gamma-ray emission from a well-known active galaxy at the time the neutrino arrived. This active galaxy is a type called a blazar, where a supermassive black hole with millions to billions of times the Sun’s mass that blasts particle jets outward in opposite directions at nearly the speed of light. Blazars are especially bright and active because one of these jets happens to point almost directly toward Earth. Fermi showed that at the time of the neutrino detection, the blazar TXS 0506+056 was the most active it had been in a decade. The discovery is a giant leap forward in a growing field called multimessenger astronomy, where new cosmic signals like neutrinos and gravitational waves are definitively linked to sources that emit light.
  • Fermi Satellite Celebrates 10 Years of Discoveries
    2018.06.11
    On June 11, NASA’s Fermi Gamma-ray Space Telescope celebrates a decade of using gamma rays, the highest-energy form of light in the cosmos, to study black holes, neutron stars, and other extreme cosmic objects and events. Fermi’s main instrument, the Large Area Telescope (LAT), has observed more than 5,000 individual gamma-ray sources. In 1949, Enrico Fermi — an Italian-American pioneer in high-energy physics and Nobel laureate for whom the mission was named — suggested that cosmic rays, particles traveling at nearly the speed of light, could be propelled by supernova shock waves. In 2013, Fermi’s LAT used gamma rays to prove these stellar remnants are at least one source of the speedy particles. Fermi’s all-sky map, produced by the LAT, has revealed two massive structures extending above and below the plane of the Milky Way. These two “bubbles” span 50,000 light-years and were probably produced by the supermassive black hole at the center of the galaxy only a few million years ago. The Gamma-ray Burst Monitor (GBM), Fermi’s secondary instrument, can see the entire sky at any instant, except the portion blocked by Earth. The satellite has observed over 2,300 gamma-ray bursts, the most luminous events in the universe. Gamma-ray bursts occur when massive stars collapse or neutron stars or black holes merge and drive jets of particles at nearly the speed of light. In those jets, matter travels at different speeds and collides, emitting gamma rays. On Aug. 17, 2017, Fermi detected a gamma-ray burst from a powerful explosion in the constellation Hydra. At almost the same time, the National Science Foundation’s Laser Interferometer Gravitational-wave Observatory detected ripples in space-time from the same event, the merger of two neutron stars. This was the first time light and gravitational waves were detected from the same source. Scientists also used another gamma-ray burst detected by Fermi to confirm Einstein’s theory that space-time is smooth and continuous.
  • Doomed Neutron Stars Create Blast of Light and Gravitational Waves
    2017.10.16
    For the first time, NASA scientists have detected light tied to a gravitational-wave event, thanks to two merging neutron stars in the galaxy NGC 4993, located about 130 million light-years from Earth in the constellation Hydra. Shortly after 8:41 a.m. EDT on Aug. 17, NASA's Fermi Gamma-ray Space Telescope picked up a pulse of high-energy light from a powerful explosion, which was immediately reported to astronomers around the globe as a short gamma-ray burst. The scientists at the National Science Foundation’s Laser Interferometer Gravitational-wave Observatory (LIGO) detected gravitational waves dubbed GW170817 from a pair of smashing stars tied to the gamma-ray burst, encouraging astronomers to look for the aftermath of the explosion. Shortly thereafter, the burst was detected as part of a follow-up analysis by ESA’s (European Space Agency’s) INTEGRAL satellite. NASA's Swift, Hubble, Chandra and Spitzer missions, along with dozens of ground-based observatories, including the NASA-funded Pan-STARRS survey, later captured the fading glow of the blast's expanding debris. Neutron stars are the crushed, leftover cores of massive stars that previously exploded as supernovas long ago. The merging stars likely had masses between 10 and 60 percent greater than that of our Sun, but they were no wider than Washington, D.C. The pair whirled around each other hundreds of times a second, producing gravitational waves at the same frequency. As they drew closer and orbited faster, the stars eventually broke apart and merged, producing both a gamma-ray burst and a rarely seen flare-up called a "kilonova." Neutron star mergers produce a wide variety of light because the objects form a maelstrom of hot debris when they collide. Merging black holes -- the types of events LIGO and its European counterpart, Virgo, have previously seen -- very likely consume any matter around them long before they crash, so we don't expect the same kind of light show. Within hours of the initial Fermi detection, LIGO and the Virgo detector at the European Gravitational Observatory near Pisa, Italy, greatly refined the event's position in the sky with additional analysis of gravitational wave data. Ground-based observatories then quickly located a new optical and infrared source -- the kilonova -- in NGC 4993. To Fermi, this appeared to be a typical short gamma-ray burst, but it occurred less than one-tenth as far away as any other short burst with a known distance, making it among the faintest known. Astronomers are still trying to figure out why this burst is so odd, and how this event relates to the more luminous gamma-ray bursts seen at much greater distances. NASA’s Swift, Hubble and Spitzer missions followed the evolution of the kilonova to better understand the composition of this slower-moving material, while Chandra searched for X-rays associated with the remains of the ultra-fast jet.
  • NASA's Fermi Catches Gamma-ray Flashes from Tropical Storms
    2017.04.24
    About a thousand times a day, thunderstorms fire off fleeting bursts of some of the highest-energy light naturally found on Earth. These events, called terrestrial gamma-ray flashes (TGFs), last less than a millisecond and produce gamma rays with tens of millions of times the energy of visible light. Since its launch in 2008, NASA's Fermi Gamma-ray Space Telescope has recorded more than 4,000 TGFs, which scientists are studying to better understand how the phenomenon relates to lightning activity, storm strength and the life cycle of storms. Now, for the first time, a team of NASA scientists has analyzed dozens of TGFs launched by the largest and strongest weather systems on the planet: tropical storms, hurricanes and typhoons. Scientists suspect TGFs arise from the strong electric fields near the tops of thunderstorms. Under certain conditions, these fields become strong enough to drive an "avalanche" of electrons upward at nearly the speed of light. When these accelerated electrons race past air molecules, their paths become deflected slightly. This change causes the electrons to emit gamma rays. The team studied 37 TGFs associated with, among other storms, typhoons Nangka (2015) and Bolaven (2012), Hurricane Paula (2010), the 2013 tropical storms Sonia and Emang and Hurricane Manuel, and the disturbance that would later become Hurricane Julio in 2014. What the scientists have learned so far is that TGFs from tropical systems do not have properties measurably different from other TGFs detected by Fermi. Weaker storms are capable of producing greater numbers of TGFs, which may arise anywhere in the storm. In more developed systems, like hurricanes and typhoons, TGFs are more common in the outermost rain bands, areas that also host the highest lightning rates in these storms. Most of the tropical storm TGFs occurred as the systems intensified. Strengthening updrafts drive clouds higher into the atmosphere where they can generate powerful electric fields, setting the stage for intense lightning and for the electron avalanches thought to produce TGFs.
  • Fermi Detects Gamma-ray Puzzle from M31
    2017.02.21
    NASA's Fermi Gamma-ray Space Telescope has found a signal at the center of the neighboring Andromeda Galaxy that could indicate the presence of the mysterious stuff known as dark matter. The gamma-ray signal is similar to one seen by Fermi at the center of our own Milky Way galaxy. Gamma rays are the highest-energy form of light, produced by the universe's most energetic phenomena. They're common in galaxies like the Milky Way because cosmic rays, particles moving near the speed of light, produce gamma rays when they interact with interstellar gas clouds and starlight. Surprisingly, the latest Fermi data shows the gamma rays in Andromeda-also known as M31-are confined to the galaxy's center instead of spread throughout. To explain this unusual distribution, scientists are proposing that the emission may come from several undetermined sources. One of them could be dark matter, an unknown substance that makes up most of the universe.
  • Fermi Sees Gamma Rays from Far Side Solar Flares
    2017.01.30
    An international science team says NASA's Fermi Gamma-ray Space Telescope has observed high-energy light from solar eruptions located on the far side of the sun, which should block direct light from these events. This apparent paradox is providing solar scientists with a unique tool for exploring how charged particles are accelerated to nearly the speed of light and move across the sun during solar flares. Fermi has seen gamma rays from the Earth-facing side of the sun, but the emission is produced by streams of particles blasted out of solar flares on the far side These particles must travel some 300,000 miles within about five minutes of the eruption to produce this light. Fermi has doubled the number of these rare events, called behind-the-limb flares, since it began scanning the sky in 2008. Its Large Area Telescope (LAT) has captured gamma rays with energies reaching 3 billion electron volts, some 30 times greater than the most energetic light previously associated with these "hidden" flares. Thanks to NASA's Solar Terrestrial Relations Observatory (STEREO) spacecraft, which were monitoring the solar far side when the eruptions occurred, the Fermi events mark the first time scientists have direct imaging of beyond-the-limb solar flares associated with high-energy gamma rays. The hidden flares occurred Oct. 11, 2013, and Jan. 6 and Sept. 1, 2014. All three events were associated with fast coronal mass ejections (CMEs), where billion-ton clouds of solar plasma were launched into space. The CME from the most recent event was moving at nearly 5 million miles an hour as it left the sun. Researchers suspect particles accelerated at the leading edge of the CMEs were responsible for the gamma-ray emission. Large magnetic field structures can connect the acceleration site with distant part of the solar surface. Because charged particles must remain attached to magnetic field lines, the research team thinks particles accelerated at the CME traveled to the sun's visible side along magnetic field lines connecting both locations. As the particles impacted the surface, they generated gamma-ray emission through a variety of processes. One prominent mechanism is thought to be proton collisions that result in a particle called a pion, which quickly decays into gamma rays.
  • Fermi Finds the Farthest Blazars
    2017.01.30
    NASA's Fermi Gamma-ray Space Telescope has identified the farthest gamma-ray blazars, a type of galaxy whose intense emissions are powered by supersized black holes. Light from the most distant object began its journey to us when the universe was 1.4 billion years old, or nearly 10 percent of its present age. Despite their youth, these far-flung blazars host some of the most massive black holes known. That they developed so early in cosmic history challenges current ideas of how supermassive black holes form and grow. Blazars constitute roughly half of the gamma-ray sources detected by Fermi's Large Area Telescope (LAT). Astronomers think their high-energy emissions are powered by matter heated and torn apart as it falls from a storage, or accretion, disk toward a supermassive black hole with a million or more times the sun's mass. A small part of this infalling material becomes redirected into a pair of particle jets, which blast outward in opposite directions at nearly the speed of light. Blazars appear bright in all forms of light, including gamma rays, the highest-energy light, when one of the jets happens to point almost directly toward us. Previously, the most distant blazars detected by Fermi emitted their light when the universe was about 2.1 billion years old. Earlier observations showed that the most distant blazars produce most of their light at energies right in between the range detected by the LAT and current X-ray satellites, which made finding them extremely difficult. Then, in 2015, the Fermi team released a full reprocessing of all LAT data, called Pass 8, that ushered in so many improvements astronomers said it was like having a brand new instrument. The LAT's boosted sensitivity at lower energies increased the chances of discovering more far-off blazars. Two of the blazars boast black holes of a billion solar masses or more. All of the objects possess extremely luminous accretion disks that emit more than two trillion times the energy output of our sun. This means matter is continuously falling inward, corralled into a disk and heated before making the final plunge to the black hole.
  • Fermi Finds Record-breaking Gamma-ray Binary
    2016.09.29
    Using data from NASA's Fermi Gamma-ray Space Telescope and other facilities, scientists have found the first gamma-ray binary in another galaxy and the most luminous one ever seen. The dual-star system, dubbed LMC P3, contains a massive star and a crushed stellar core that interact to produce a cyclic flood of gamma rays, the highest-energy form of light. Gamma-ray binaries are rare -- only six are known in our own galaxy, and one remains undetected by Fermi. The systems are prized because their gamma-ray output changes significantly during each orbit and sometimes over longer time scales. This variation lets astronomers study many of the emission processes common to other gamma-ray sources in unique detail. The systems contain either a neutron star or a black hole and radiate most of their energy in the form of gamma rays. Remarkably, LMC P3 is the most luminous such system known in gamma rays, X-rays, radio waves and visible light, and it's only the second one discovered with Fermi. LMC P3 lies within a supernova remnant located in the Large Magellanic Cloud (LMC), a small nearby galaxy about 163,000 light-years away. In 2012, scientists using NASA's Chandra X-ray Observatory found a strong X-ray source within the remnant and showed that it was orbiting a hot, young star many times the sun's mass. The researchers concluded the compact object was either a neutron star or a black hole and classified the system as a high-mass X-ray binary (HMXB). In 2015, a team led by Robin Corbet at NASA's Goddard Space Flight Center began looking for new gamma-ray binaries in Fermi data by searching for the periodic changes characteristic of these systems. The scientists discovered a 10.3-day cyclic change centered near one of several gamma-ray point sources recently identified in the LMC. One of them, called P3, was not linked to objects seen at any other wavelengths but was located near the HMXB. Were they the same object? Observations from NASA's Swift satellite clearly reveal the same 10.3-day cycle seen in gamma rays by Fermi. They also indicate that the brightest X-ray emission occurs opposite the gamma-ray peak, so when one reaches maximum the other is at minimum. Radio data exhibit the same period and out-of-phase relationship with the gamma-ray peak, confirming that LMC P3 is indeed the same system investigated by Chandra. Prior to Fermi's launch, gamma-ray binaries were expected to be more numerous than they've turned out to be. It's a puzzle because hundreds of HMXBs are cataloged, and all of them are thought to have originated as gamma-ray binaries following the supernova that formed the compact object. Its possible gamma-ray binaries may form only from neutron stars born with the fastest spins, which would enhance their ability to produce gamma rays.
  • Fermi Helps Link a Cosmic Neutrino to a Blazar Outburst
    2016.04.28
    Nearly 10 billion years ago, the black hole at the center of a distant galaxy produced a powerful outburst, and light from this blast began arriving at Earth in 2012. Astronomers using data from NASA's Fermi Gamma-ray Space Telescope and other space- and ground-based observatories have shown that a record-breaking neutrino seen around the same time likely was born in the same event. Neutrinos are the fastest, lightest, most unsociable and least understood fundamental particles. The study provides the first plausible association between a single extragalactic object and a high-energy cosmic neutrino. Although neutrinos far outnumber all the atoms in the universe, they rarely interact with matter. While this property makes them hard to detect, it lets neutrinos make a fast exit from places where light cannot easily escape -- such as the core of a collapsing star -- and zip across the universe almost completely unimpeded. Neutrinos can provide information about processes and environments that simply aren't available through a study of light alone. The IceCube Neutrino Observatory, built into a cubic kilometer of clear glacial ice at the South Pole, detects neutrinos when they interact with atoms in the ice. Some of the most extreme particles detected by IceCube receive nicknames based on characters on the children's TV series "Sesame Street." On Dec. 4, 2012, IceCube detected an event known as Big Bird, a neutrino with an energy exceeding 2 quadrillion electron volts (PeV), the highest-energy neutrino ever detected at the time. But the best IceCube position only narrowed the source to a patch of the southern sky about 32 degrees across, equivalent to the apparent size of 64 full moons. In the summer of 2012, Fermi's Large Area Telescope (LAT) witnessed the onset of a dramatic brightening of PKS B1424-418, an active galaxy classified as a gamma-ray blazar. An active galaxy is an otherwise typical galaxy with a compact and unusually bright core; this excess luminosity is produced by matter falling toward a supermassive black hole weighing millions of times the mass of our sun. As it approaches the black hole, some of the material becomes channeled into particle jets moving outward in opposite directions at nearly the speed of light. In blazars, one of these jets happens to point almost directly toward Earth. During the year-long outburst, PKS B1424-418 shone between 15 and 30 times brighter in gamma rays than its average before the eruption. The blazar is located within the Big Bird source region, but so are many other active galaxies detected by Fermi. Was it the culprit? Astronomers investigating the link turned to the TANAMI project, which since 2007 has routinely monitored dozens of active galaxies in the southern sky. The program includes regular radio observations using the Australian Long Baseline Array (LBA) and associated telescopes in Chile, South Africa, New Zealand and Antarctica. When networked together, they operate as a single radio telescope more than 6,000 miles across and provide a unique high-resolution look into the jets of active galaxies. Three radio observations of PKS B1424-418 between 2011 and 2013 cover the period of the Fermi outburst. They reveal that the core of the galaxy's jet had brightened by about four times. No other galaxy observed by TANAMI over the life of the program has exhibited such a dramatic change. The team suggests the PKS B1424-418 outburst and Big Bird are connected, calculating only a 5-percent probability the two events occurred by chance alone. Using data from Fermi, NASA’s Swift and WISE satellites, the LBA and other facilities, the researchers determined how the energy of the eruption was distributed across the electromagnetic spectrum and showed that it was sufficiently powerful to produce a neutrino at PeV energies.
  • NASA's Fermi Preps to Narrow Down Gravitational Wave Sources
    2016.04.18
    On Sept. 14, waves of energy traveling for more than a billion years gently rattled space-time in the vicinity of Earth. The disturbance, produced by a pair of merging black holes, was captured by the Laser Interferometer Gravitational-Wave Observatory (LIGO) facilities in Hanford, Washington, and Livingston, Louisiana. This event marked the first-ever detection of gravitational waves and opens a new scientific window on how the universe works. Less than half a second later, the Gamma-ray Burst Monitor (GBM) on NASA's Fermi Gamma-ray Space Telescope picked up a brief, weak burst of high-energy light consistent with the same part of the sky. Analysis of this burst suggests just a 0.2-percent chance of simply being random coincidence. Gamma-rays arising from a black hole merger would be a landmark finding because black holes are expected to merge “cleanly,” without producing any sort of light. Detecting light from a gravitational wave source will enable a much deeper understanding of the event. With its wide energy range and large field of view, the GBM is the premier instrument for detecting light from short gamma-ray bursts (GRBs), which last less than two seconds. They are widely thought to occur when orbiting compact objects, like neutron stars and black holes, spiral inward and crash together. These same systems also are suspected to be prime producers of gravitational waves. Currently, gravitational wave observatories possess relatively blurry vision. For the September event, dubbed GW150914 after the date, LIGO scientists could only trace the source to an arc of sky spanning an area of about 600 square degrees, comparable to the angular area on Earth occupied by the United States. Assuming the GBM burst is connected to this event, the GBM localization and Fermi's view of Earth combine to reduce the LIGO search area by about two-thirds, to 200 square degrees. With a burst better placed for the GBM’s detectors, or one bright enough to be seen by Fermi’s Large Area Telescope, even greater improvements are possible. Black hole mergers were not expected to emit significant X-ray or gamma-ray signals because orbiting gas is needed to generate light. Theorists expected any gas around binary black holes would have been swept up long before their final plunge. For this reason, some astronomers view the GBM burst as most likely a coincidence and unrelated to GW150914. Others have developed alternative scenarios where merging black holes could create observable gamma-ray emission. It will take further detections to clarify what really happens when black holes collide.
  • NASA's Fermi Mission Sharpens its High-energy View
    2016.01.07
    Major improvements to methods used to process observations from NASA's Fermi Gamma-ray Space Telescope have yielded an expanded, higher-quality set of data that allows astronomers to produce the most detailed census of the sky yet made at extreme energies. A new sky map reveals hundreds of these sources, including 12 that produce gamma rays with energies exceeding a trillion times the energy of visible light. The survey also discovered four dozen new sources that remain undetected at any other wavelength. By carefully reexamining every gamma-ray and particle detection by the LAT since Fermi's 2008 launch, scientists improved their knowledge of the detector's response to each event and to the background environment in which it was measured. This enabled the Fermi team to find many gamma rays that previously had been missed while simultaneously improving the LAT's ability to determine the directions of incoming gamma rays. The improved data, known as Pass 8, effectively sharpens the LAT's view while also significantly widening its useful energy range. Using 61,000 Pass 8 gamma rays collected over 80 months, Marco Ajello and his colleagues constructed a map of the entire sky at energies ranging from 50 billion (GeV) to 2 trillion electron volts (TeV). For comparison, the energy of visible light ranges from about 2 to 3 electron volts. The Fermi team catalogued 360 individual gamma-ray sources, about 75 percent of which are blazars -- distant galaxies sporting jets powered by supermassive black holes. The highest-energy sources, which are all located within our galaxy, are mostly the remnants of supernova explosions and pulsar wind nebulae, places where rapidly rotating neutron stars accelerate particles to near the speed of light. A famous example, the Crab Nebula, tops the list of the highest-energy Fermi sources, producing a steady drizzle of gamma rays exceeding 1 TeV. Astronomers think these very high-energy gamma rays are produced when lower-energy light collides with accelerated particles. This results in a small energy loss for the particle and a big gain for the light, transforming it into a gamma ray. For the first time, Fermi data now extend to energies previously seen only by ground-based detectors. Because ground-based telescopes have much smaller fields of view than the LAT, which scans the whole sky every three hours, they have detected only about a quarter of the objects in the new catalog. This study provides ground facilities with more than 280 new targets for follow-up observations.
  • NASA's Fermi Satellite Kicks Off a Blazar Bonanza
    2015.12.15
    A long time ago in a galaxy half the universe away, a flood of high-energy gamma rays began its journey to Earth. When they arrived in April, NASA's Fermi Gamma-ray Space Telescope caught the outburst, which helped two ground-based gamma-ray observatories detect some of the highest-energy light ever seen from a galaxy so distant. Astronomers had assumed that light at different energies came from regions at different distances from the black hole. Gamma rays, the highest-energy form of light, were thought to be produced closest in. But observations across the spectrum suggest that light at all wavelengths came from a single region located far away roughly five light-years from the black hole, which is greater than the distance between our sun and the nearest star. The gamma rays came from a galaxy known as PKS 1441+25, a type of active galaxy called a blazar. Located toward the constellation Boötes, the galaxy is so far away its light takes 7.6 billion years to reach us. At its heart lies a monster black hole with a mass estimated at 70 million times the sun's and a surrounding disk of hot gas and dust. If placed at the center of our solar system, the black hole's event horizon -- the point beyond which nothing can escape -- would extend almost to the orbit of Mars. As material in the disk falls toward the black hole, some of it forms dual particle jets that blast out of the disk in opposite directions at nearly the speed of light. Blazars are so bright in gamma rays because one jet points almost directly toward us, giving astronomers a view straight into the black hole's dynamic and poorly understood realm. In April, PKS 1441+25 underwent a major eruption. Luigi Pacciani at the Italian National Institute for Astrophysics in Rome was leading a project to catch blazar flares in their earliest stages in collaboration with the Major Atmospheric Gamma-ray Imaging Cerenkov experiment (MAGIC), located on La Palma in the Canary Islands. Using public Fermi data, Pacciani discovered the outburst and immediately alerted the astronomical community. Fermi's Large Area Telescope revealed gamma rays up to 33 billion electron volts (GeV), reaching into the highest-energy part of the instrument's detection range. For comparison, visible light has energies between about 2 and 3 electron volts. Following up on the Fermi alert, the MAGIC team turned to the blazar and detected gamma rays with energies ranging from 40 to 250 GeV. Because this galaxy is so far away, we didn't have a strong expectation of detecting gamma rays with energies this high. That’s because distance matters for very high-energy gamma rays -- they convert into particles when they collide with lower-energy light. The visible and ultraviolet light from stars shining throughout the history of the universe forms a remnant glow called the extragalactic background light (EBL). For gamma rays, this is a cosmic gauntlet they must pass through to be detected at Earth. When a gamma ray encounters starlight, it transforms into an electron and a positron and is lost to astronomers. The farther away the blazar is, the less likely its highest-energy gamma rays will survive to be detected. Following the MAGIC discovery, VERITAS also detected gamma rays with energies approaching 200 GeV. PKS 1441+25 is one of only two such distant sources for which gamma rays with energies above 100 GeV have been observed. Its dramatic flare provides a powerful glimpse into the intensity of the EBL from near-infrared to near-ultraviolet wavelengths and suggests that galaxy surveys have identified most of the sources responsible for it.
  • Fermi finds the first extragalactic gamma-ray pulsar
    2015.11.12
    Researchers using NASA's Fermi Gamma-ray Space Telescope have discovered the first gamma-ray pulsar in a galaxy other than our own. The object sets a new record for the most luminous gamma-ray pulsar known. The pulsar lies in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud, a small galaxy that orbits our Milky Way and is located 163,000 light-years away. The Tarantula Nebula is the largest, most active and most complex star-formation region in our galactic neighborhood. It was identified as a bright source of gamma rays, the highest-energy form of light, early in the Fermi mission. Astronomers initially attributed this glow to collisions of subatomic particles accelerated in the shock waves produced by supernova . However, the discovery of gamma-ray pulses from a previously known pulsar named PSR J0540-6919 shows that it is responsible for roughly half of the gamma-ray brightness previously thought to come from the nebula. Gamma-ray pulses from J0540-6919 have 20 times the intensity of the previous record-holder, the pulsar in the famous Crab Nebula. Yet they have roughly similar levels of radio, optical and X-ray emission. Accounting for these differences will guide astronomers to a better understanding of the extreme physics at work in young pulsars.
  • Fermi Spots a Record Flare from Blazar 3C 279
    2015.07.10
    Five billion years ago, a great disturbance rocked a region near the monster black hole at the center of galaxy 3C 279. On June 14, the pulse of high-energy light produced by this event finally arrived at Earth, setting off detectors aboard NASA's Fermi Gamma-ray Space Telescope and other satellites. Astronomers around the world turned instruments toward the galaxy to observe this brief but record-setting flare in greater detail. 3C 279 is a famous blazar, a galaxy whose high-energy activity is powered by a central supermassive black hole weighing up to a billion times the sun's mass and roughly the size of our planetary system. As matter falls toward the black hole, some particles race away at nearly the speed of light along a pair of jets pointed in opposite directions. What makes a blazar so bright is that one of these particle jets happens to be aimed almost straight at us. The brightest persistent source in the gamma-ray sky is the Vela pulsar, which is about 1,000 light-years away. 3C 279 is millions of times farther off, but during this flare it became four times brighter than Vela. This corresponds to a tremendous energy release, and one that cannot be sustained for long. The galaxy rapidly brightened in less than a day, peaked on June 16, and dimmed to normal gamma-ray levels by June 18. The rapid fading is why astronomers rush to collect data as soon as they detect a blazar flare. The Italian Space Agency's AGILE gamma-ray satellite first reported the flare, followed by Fermi. Rapid follow-up observations were made by NASA's Swift satellite and the European Space Agency's INTEGRAL spacecraft, which just happened to be looking in the right direction, along with optical and radio telescopes on the ground.
  • Astronomers Predict Cosmic Light Show from 2018 Stellar Encounter
    2015.07.02
    Astronomers are gearing up for high-energy fireworks coming in early 2018, when a stellar remnant the size of a city meets one of the brightest stars in our galaxy. The cosmic light show will occur when a pulsar discovered by NASA's Fermi Gamma-ray Space Telescope swings by its companion star. Scientists plan a global campaign to watch the event from radio wavelengths to the highest-energy gamma rays detectable. The pulsar, known as J2032+4127 (J2032 for short), is the crushed core of a massive star that exploded as a supernova. It is a magnetized ball about 12 miles across, or about the size of Washington, weighing almost twice the sun's mass and spinning seven times a second. J2032's rapid spin and strong magnetic field together produce a lighthouse-like beam detectable when it sweeps our way. The pulsar orbits a massive companion named MT91 213. Classified as a Be star, the companion is 15 times the mass of the sun and shines 10,000 times brighter. Be stars drive strong outflows, called stellar winds, and are embedded in large disks of gas and dust. Following an elongated orbit lasting about 25 years, the pulsar passes closest to its partner once each circuit. Whipping around its companion in early 2018, the pulsar will plunge through the surrounding disk and trigger astrophysical fireworks. It will serve as a probe to help astronomers measure the massive star's gravity, magnetic field, stellar wind and disk properties. Read more at http://www.nasa.gov/feature/goddard/astronomers-predict-fireworks-from-rare-stellar-encounter-in-2018
  • Turning Black Holes into Dark Matter Labs
    2015.06.23
    A new computer simulation tracking dark matter particles in the extreme gravity of a black hole shows that strong, potentially observable gamma-ray light can be produced. Detecting this emission would provide astronomers with a new tool for understanding both black holes and the nature of dark matter, an elusive substance accounting for most of the mass of the universe that neither reflects, absorbs nor emits light. Jeremy Schnittman, an astrophysicist at NASA's Goddard Space Flight Center, developed a computer simulation to follow the orbits of hundreds of millions of dark matter particles, as well as the gamma rays produced when they collide, in the vicinity of a black hole. He found that some gamma rays escaped with energies far exceeding what had been previously regarded as theoretical limits. In the simulation, dark matter takes the form of Weakly Interacting Massive Particles, or WIMPS, now widely regarded as the leading candidate class. In this model, WIMPs that crash into other WIMPs mutually annihilate and convert into gamma rays, the most energetic form of light. But these collisions are extremely rare under normal circumstances. Over the past few years, theorists have turned to black holes as dark matter concentrators, where WIMPs can be forced together in a way that increases both the rate and energies of collisions. The concept is a variant of the Penrose process, first identified in 1969 by British astrophysicist Sir Roger Penrose as a mechanism for extracting energy from a spinning black hole. The faster it spins, the greater the potential energy gain. In this process, all of the action takes place outside the black hole's event horizon, the boundary beyond which nothing can escape, in a flattened region called the ergosphere. Within the ergosphere, the black hole's rotation drags space-time along with it and everything is forced to move in the same direction at nearly speed of light. This creates a natural laboratory more extreme than any possible on Earth. Previous work indicated that the maximum gamma-ray energy from the collisional version of the Penrose process was only about 1.3 times the rest mass of the annihilating particles. In addition, only a small portion of high-energy gamma rays managed to escape the ergosphere. These results suggested that a conclusive annihilation signal might never be seen from a supermassive black hole. However, earlier work made simplifying assumptions about the locations of the highest-energy collisions. Schnittman's model instead tracks the positions and properties of hundreds of millions of randomly distributed particles as they collide and annihilate near a black hole. The new model reveals processes that produce gamma rays with much higher energies, as well as a better likelihood of escape and detection, than ever thought possible. He identified previously unrecognized trajectories where collisions produce gamma rays with a peak energy 14 times the rest mass of the annihilating particles. The simulation tells astronomers that there is an astrophysically interesting signal they may be able to detect as gamma-ray telescopes improve.
  • NASA's Fermi Helps Scientists Study Gamma-ray Thunderstorms
    2014.12.15
    Merging data on high-energy bursts seen on Earth by NASA's Fermi Gamma-ray Space Telescope with data from ground-based radar and lightning detectors, scientists have completed the most detailed analysis to date of the types of thunderstorms producing terrestrial gamma-ray flashes, or TGFs. TGFs occur unpredictably and fleetingly, with durations less than a thousandth of a second, and remain poorly understood. Yet the gamma rays they produce rank among the highest-energy light naturally produced on Earth. Earlier Fermi studies helped uncover lightning-like radio signals emitted by TGFs. This made it possible to use ground-based lightning location networks to pin down storms producing the flashes, opening the door to a deeper understanding of the meteorology powering these extreme events. Scientists gathered a sample of nearly 900 Fermi TGFs accurately located by ground networks, which can pinpoint the location of lightning discharges -- and the corresponding signals from TGFs -- to within 6 miles (10 km) anywhere on the globe. From this group, they identified 24 TGFs that occurred within areas covered by Next Generation Weather Radar (NEXRAD) sites. The researchers found that even weak and marginally electrified storms are capable of producing TGFs. The new study also confirms previous findings indicating that TGFs tend to occur near the highest parts of a thunderstorm, between about 7 and 9 miles (11 to 14 kilometers) high. However, TGFs associated with lightning at lower altitudes would be so weakened by traveling a longer path through the atmosphere that Fermi couldn't detect them. If true, the estimated number of 1,100 TGFs occurring each day may be much larger than previously thought.
  • NASA's Fermi Catches a 'Transformer' Pulsar
    2014.07.22
    In late June 2013, an exceptional binary system containing a rapidly spinning neutron star underwent a dramatic change in behavior never before observed. The pulsar's radio beacon vanished, while at the same time the system brightened fivefold in gamma rays, the most powerful form of light, according to measurements by NASA's Fermi Gamma-ray Space Telescope. The system, known as AY Sextantis, is located about 4,400 light-years away in the constellation Sextans. It pairs a 1.7-millisecond pulsar named PSR J1023+0038 — J1023 for short — with a star containing about one-fifth the mass of the sun. The stars complete an orbit in only 4.8 hours, which places them so close together that the pulsar will gradually evaporate its companion. To better understand J1023's spin and orbital evolution, the system was routinely monitored in radio. These observations revealed that the pulsar's radio signal had turned off and prompted the search for an associated change in its gamma-ray properties. What's happening, astronomers say, are the last sputtering throes of the pulsar spin-up process. Researchers regard the system as a unique laboratory for understanding how millisecond pulsars form and for studying details of how accretion takes place on neutron stars. In J1023, the stars are close enough that a stream of gas flows from the sun-like star toward the pulsar. The pulsar's rapid rotation and intense magnetic field are responsible for both the radio beam and its powerful pulsar wind. When the radio beam is detectable, the pulsar wind holds back the companion's gas stream, preventing it from approaching too closely. But now and then the stream surges, pushing its way closer to the pulsar and establishing an accretion disk. When gas from the disk falls to an altitude of about 50 miles (80 km), processes involved in creating the radio beam are either shut down or, more likely, obscured. Some of the gas may be accelerated outward at nearly the speed of light, forming dual particle jets firing in opposite directions. Shock waves within and along the periphery of these jets are a likely source of the bright gamma-ray emission detected by Fermi.
  • Black Widow Pulsars Consume Their Mates
    2014.02.20
    Black widow spiders and their Australian cousins, known as redbacks, are notorious for an unsettling tendency to kill and devour their male partners. Astronomers have noted similar behavior among two rare breeds of binary system that contain rapidly spinning neutron stars, also known as pulsars.

    The essential features of black widow and redback binaries are that they place a normal but very low-mass star in close proximity to a millisecond pulsar, which has disastrous consequences for the star. Black widow systems contain stars that are both physically smaller and of much lower mass than those found in redbacks.

    So far, astronomers have found at least 18 black widows and nine redbacks within the Milky Way, and additional members of each class have been discovered within the dense globular star clusters that orbit our galaxy.

    One black widow system, named PSR J1311-3430 and discovered in 2012, sets the record for the tightest orbit of its class and contains one of the heaviest neutron stars known. The pulsar's featherweight companion, which is only a dozen or so times the mass of Jupiter and just 60 percent of its size, completes an orbit every 93 minutes – less time than it takes to watch most movies.

    The side of the star facing the pulsar is heated to more than 21,000 degrees Fahrenheit (nearly 12,000 C), or more than twice as hot as the sun's surface. Recent studies allow a range of values extending down to 2 solar masses for the pulsar, making it one of the most massive neutron stars known.

    Watch the video to learn more about this system and its discovery from some of the scientists involved.

  • Highlights of Fermi's First Five Years
    2013.08.21
    This compilation summarizes the wide range of science from the first five years of NASA's Fermi Gamma-ray Space Telescope. Fermi is a NASA observatory designed to reveal the high-energy universe in never-before-seen detail. Launched in 2008, Fermi continues to give astronomers a unique tool for exploring high-energy processes associated with solar flares, spinning neutron stars, outbursts from black holes, exploding stars, supernova remnants and energetic particles to gain insight into how the universe works.

    Fermi detects gamma rays, the most powerful form of light, with energies thousands to billions of times greater than the visible spectrum.

    The mission has discovered pulsars, proved that supernova remnants can accelerate particles to near the speed of light, monitored eruptions of black holes in distant galaxies, and found giant bubbles linked to the central black hole in our own galaxy.

    From blazars to thunderstorms, from dark matter to supernova remnants, catch the highlights of NASA Fermi’s first five years in space.

    View all the Fermi-related media from the last 5 years in the Fermi Gallery.

    For more information about Fermi, visit NASA's Fermi webpage.

  • When Fermi Dodged a 1.5-ton Bullet
    2013.04.30
    NASA scientists don't often learn that their spacecraft is at risk of crashing into another satellite. But when Julie McEnery, the project scientist for NASA's Fermi Gamma-ray Space Telescope, checked her email on March 29, 2012, she found herself facing this precise situation.

    While Fermi is in fine shape today, continuing its mission to map the highest-energy light in the universe, the story of how it sidestepped a potential disaster offers a glimpse at an underappreciated aspect of managing a space mission: orbital traffic control.

    As McEnery worked through her inbox, an automatically generated report arrived from NASA's Robotic Conjunction Assessment Risk Analysis (CARA) team based at NASA's Goddard Space Flight Center in Greenbelt, Md. On scanning the document, she discovered that Fermi was just one week away from an unusually close encounter with Cosmos 1805, a dead Cold-War era spy satellite.

    The two objects, speeding around Earth at thousands of miles an hour in nearly perpendicular orbits, were expected to miss each other by a mere 700 feet.

    Although the forecast indicated a close call, satellite operators have learned the hard way that they can't be too careful. The uncertainties in predicting spacecraft positions a week into the future can be much larger than the distances forecast for their closest approach.

    With a speed relative to Fermi of 27,000 mph, a direct hit by the 3,100-pound Cosmos 1805 would release as much energy as two and a half tons of high explosives, destroying both spacecraft.

    The update on Friday, March 30, indicated that the satellites would occupy the same point in space within 30 milliseconds of each other. Fermi would have to move out of the way if the threat failed to recede. Because Fermi's thrusters were designed to de-orbit the satellite at the end of its mission, they had never before been used or tested, adding a new source of anxiety for the team.

    By Tuesday, April 3, the close approach was certain, and all plans were in place for firing Fermi's thrusters. The maneuver was performed by the spacecraft based on previously developed procedures. Fermi fired all thrusters for one second and was back doing science within the hour.

    Watch this video on YouTube.

  • Fermi Traces a Celestial Spirograph
    2013.02.27
    NASA's Fermi Gamma-ray Space Telescope orbits our planet every 95 minutes, building up increasingly deeper views of the universe with every circuit. Its wide-eyed Large Area Telescope (LAT) sweeps across the entire sky every three hours, capturing the highest-energy form of light — gamma rays — from sources across the universe. These range from supermassive black holes billions of light-years away to intriguing objects in our own galaxy, such as X-ray binaries, supernova remnants and pulsars.

    Now a Fermi scientist has transformed LAT data of a famous pulsar into a mesmerizing movie that visually encapsulates the spacecraft's complex motion.

    Pulsars are neutron stars, the crushed cores of massive suns that destroyed themselves when they ran out of fuel, collapsed and exploded. The blast simultaneously shattered the star and compressed its core into a body as small as a city yet more massive than the sun. One pulsar, called Vela, shines especially bright for Fermi. It spins 11 times a second and is the brightest persistent source of gamma rays the LAT sees.

    The movie renders Vela's position in a fisheye perspective, where the middle of the pattern corresponds to the central and most sensitive portion of the LAT's field of view. The edge of the pattern is 90 degrees away from the center and well beyond what scientists regard as the effective limit of the LAT's vision. The movie tracks both Vela's position relative to the center of the LAT's field of view and the instrument's exposure of the pulsar during the first 51 months of Fermi's mission, from Aug. 4, 2008, to Nov. 15, 2012.

    The pattern Vela traces reflects numerous motions of the spacecraft. The first is Fermi's 95-minute orbit around Earth, but there's another, subtler motion related to it. The orbit itself also rotates, a phenomenon called precession. Similar to the wobble of an unsteady top, Fermi's orbital plane makes a slow circuit around Earth every 54 days.

    In order to capture the entire sky every two orbits, scientists deliberately nod the LAT in a repeating pattern from one orbit to the next. It first looks north on one orbit, south on the next, and then north again. Every few weeks, the LAT deviates from this pattern to concentrate on particularly interesting targets, such as eruptions on the sun, brief but brilliant gamma-ray bursts associated with the birth of stellar-mass black holes, and outbursts from supermassive black holes in distant galaxies.

    The Vela movie captures one other Fermi motion. The spacecraft rolls to keep the sun from shining on and warming up the LAT's radiators, which regulate its temperature by bleeding excess heat into space.

  • Fermi Proves Supernova Remnants Produce Cosmic Rays
    2013.02.14
    A new study using observations from NASA's Fermi Gamma-ray Space Telescope reveals the first clear-cut evidence that the expanding debris of exploded stars produces some of the fastest-moving matter in the universe. This discovery is a major step toward meeting one of Fermi's primary mission goals.

    Cosmic rays are subatomic particles that move through space at nearly the speed of light. About 90 percent of them are protons, with the remainder consisting of electrons and atomic nuclei. In their journey across the galaxy, the electrically charged particles become deflected by magnetic fields. This scrambles their paths and makes it impossible to trace their origins directly.

    Through a variety of mechanisms, these speedy particles can lead to the emission of gamma rays, the most powerful form of light and a signal that travels to us directly from its sources.

    Two supernova remnants, known as IC 443 and W44, are expanding into cold, dense clouds of interstellar gas. This material emits gamma rays when struck by high-speed particles escaping the remnants.

    Scientists have been unable to ascertain which particle is responsible for this emission because cosmic-ray protons and electrons give rise to gamma rays with similar energies. Now, after analyzing four years of data, Fermi scientists see a gamma-ray feature from both remnants that, like a fingerprint, proves the culprits are protons.

    When cosmic-ray protons smash into normal protons, they produce a short-lived particle called a neutral pion. The pion quickly decays into a pair of gamma rays. This emission falls within a specific band of energies associated with the rest mass of the neutral pion, and it declines steeply toward lower energies.

    Detecting this low-end cutoff is clear proof that the gamma rays arise from decaying pions formed by protons accelerated within the supernova remnants.

    In 1949, the Fermi telescope's namesake, physicist Enrico Fermi, suggested that the highest-energy cosmic rays were accelerated in the magnetic fields of interstellar gas clouds. In the decades that followed, astronomers showed that supernova remnants were the galaxy's best candidate sites for this process.?

    A charged particle trapped in a supernova remnant's magnetic field moves randomly throughout it and occasionally crosses through the explosion's leading shock wave. Each round trip through the shock ramps up the particle's speed by about 1 percent. After many crossings, the particle obtains enough energy to break free and escapes into the galaxy as a newborn cosmic ray.

    The Fermi discovery builds on a strong hint of neutral pion decay in W44 observed by the Italian Space Agency's AGILE gamma-ray observatory and published in late 2011.

  • Fermi Improves Its Vision For Thunderstorm Gamma-ray Flashes
    2012.12.06
    Thanks to improved data analysis techniques and a new operating mode, the Gamma-ray Burst Monitor (GBM) aboard NASA's Fermi Gamma-ray Space Telescope is now 10 times better at catching the brief outbursts of high-energy light mysteriously produced above thunderstorms.

    The outbursts, known as terrestrial gamma-ray flashes (TGFs), last only a few thousandths of a second, but their gamma rays rank among the highest-energy light that naturally occurs on Earth. The enhanced GBM discovery rate helped scientists show most TGFs also generate a strong burst of radio waves, a finding that will change how scientists study this poorly understood phenomenon.

    Lightning emits a broad range of very low frequency (VLF) radio waves, often heard as pop-and-crackle static when listening to AM radio. The World Wide Lightning Location Network (WWLLN), a research collaboration operated by the University of Washington in Seattle, routinely detects these radio signals and uses them to pinpoint the location of lightning discharges anywhere on the globe to within about 12 miles (20 km).

    Scientists have known for a long time TGFs were linked to strong VLF bursts, but they interpreted these signals as originating from lightning strokes somehow associated with the gamma-ray emission.

    "Instead, we've found when a strong radio burst occurs almost simultaneously with a TGF, the radio emission is coming from the TGF itself," said co-author Michael Briggs, a member of the GBM team.

    The researchers identified much weaker radio bursts that occur up to several thousandths of a second before or after a TGF. They interpret these signals as intracloud lightning strokes related to, but not created by, the gamma-ray flash.

    Scientists suspect TGFs arise from the strong electric fields near the tops of thunderstorms. Under certain conditions, the field becomes strong enough that it drives a high-speed upward avalanche of electrons, which give off gamma rays when they are deflected by air molecules.

    "What's new here is that the same electron avalanche likely responsible for the gamma-ray emission also produces the VLF radio bursts, and this gives us a new window into understanding this phenomenon," said Joseph Dwyer, a physics professor at the Florida Institute of Technology in Melbourne, Fla., and a member of the study team.

    Because the WWLLN radio positions are far more precise than those based on Fermi's orbit, scientists will develop a much clearer picture of where TGFs occur and perhaps which types of thunderstorms tend to produce them.

  • NASA's Fermi Explores the Early Universe
    2012.11.01
    Astronomers using data from NASA's Fermi Gamma-ray Space Telescope have made the most accurate measurement of starlight in the universe and used it to establish the total amount of light from all of the stars that have ever shone, accomplishing a primary mission goal.

    Gamma rays are the most energetic form of light. Since Fermi's launch in 2008, its Large Area Telescope (LAT) observes the entire sky in high-energy gamma rays every three hours, creating the most detailed map of the universe ever known at these energies.

    The total sum of starlight in the cosmos is known to astronomers as the extragalactic background light (EBL). To gamma rays, the EBL functions as a kind of cosmic fog. Ajello and his team investigated the EBL by studying gamma rays from 150 blazars, or galaxies powered by black holes, that were strongly detected at energies greater than 3 billion electron volts (GeV), or more than a billion times the energy of visible light.

    As matter falls toward a galaxy's supermassive black hole, some of it is accelerated outward at almost the speed of light in jets pointed in opposite directions. When one of the jets happens to be aimed in the direction of Earth, the galaxy appears especially bright and is classified as a blazar.

    Gamma rays produced in blazar jets travel across billions of light-years to Earth. During their journey, the gamma rays pass through an increasing fog of visible and ultraviolet light emitted by stars that formed throughout the history of the universe.

    Occasionally, a gamma ray collides with starlight and transforms into a pair of particles — an electron and its antimatter counterpart, a positron. Once this occurs, the gamma ray light is lost. In effect, the process dampens the gamma-ray signal in much the same way as fog dims a distant lighthouse.

    From studies of nearby blazars, scientists have determined how many gamma rays should be emitted at different energies. More distant blazars show fewer gamma rays at higher energies — especially above 25 GeV — thanks to absorption by the cosmic fog.

    The farthest blazars are missing most of their higher-energy gamma rays.

    The researchers then determined the average gamma-ray attenuation across three distance ranges between 9.6 billion years ago and today.

    From this measurement, the scientists were able to estimate the fog's thickness. To account for the observations, the average stellar density in the cosmos is about 1.4 stars per 100 billion cubic light-years. To put this in another way, the average distance between stars in the universe is about 4,150 light-years.

  • NASA's Fermi Detects the Highest-Energy Light from a Solar Flare
    2012.06.11
    During a powerful solar blast in March, NASA's Fermi Gamma-ray Space Telescope detected the highest-energy light ever associated with an eruption on the sun. The discovery heralds Fermi's new role as a solar observatory, a powerful new tool for understanding solar outbursts during the sun's maximum period of activity.

    "For most of Fermi's four years in orbit, its Large Area Telescope (LAT) saw the sun as a faint, steady gamma-ray source thanks to the impacts of high-speed particles called cosmic rays," said Nicola Omodei, an astrophysicist at Stanford University in California. "Now we're beginning to see what the sun itself can do."

    A solar flare is an explosive blast of light and charged particles. The powerful March 7 flare, which earned a classification of X5.4 based on the peak intensity of its X-rays, is the strongest eruption so far observed by Fermi's LAT. The flare produced such an outpouring of gamma rays — a form of light with even greater energy than X-rays — that the sun briefly became the brightest object in the gamma-ray sky.

    At the flare's peak, the LAT detected gamma rays with two billion times the energy of visible light, or about 4 billion electron volts (GeV), easily setting a record for the highest-energy light ever detected during or just after a solar flare. The flux of high-energy gamma rays, defined as those with energies beyond 100 million electron volts (MeV), was 1,000 times greater than the sun's steady output.

    The March 7 flare also is notable for the persistence of its gamma-ray emission. Fermi's LAT detected high-energy gamma rays for about 20 hours, two and a half times longer than any event on record.

    Additionally, the event marks the first time a greater-than-100-MeV gamma-ray source has been localized to the sun's disk, thanks to the LAT's keen angular resolution.

    Flares and other eruptive solar events produce gamma rays by accelerating charged particles, which then collide with matter in the sun's atmosphere and visible surface. For instance, interactions among protons result in short-lived subatomic particles called pions, which produce high-energy gamma rays when they decay. Nuclei excited by collisions with lower-energy ions give off characteristic gamma rays as they settle down. Accelerated electrons emit gamma rays as they collide with protons and atomic nuclei.

    Solar eruptions are now on the rise as the sun progresses toward the peak of its roughly 11-year-long activity cycle, now expected in mid-2013.

  • Fermi Observations of Dwarf Galaxies Provide New Insights on Dark Matter
    2012.04.02
    There's more to the cosmos than meets the eye. About 80 percent of the matter in the universe is invisible to telescopes, yet its gravitational influence is manifest in the orbital speeds of stars around galaxies and in the motions of clusters of galaxies. Yet, despite decades of effort, no one knows what this "dark matter" really is. Many scientists think it's likely that the mystery will be solved with the discovery of new kinds of subatomic particles, types necessarily different from those composing atoms of the ordinary matter all around us. The search to detect and identify these particles is underway in experiments both around the globe and above it.

    Scientists working with data from NASA's Fermi Gamma-ray Space Telescope have looked for signals from some of these hypothetical particles by zeroing in on 10 small, faint galaxies that orbit our own. Although no signals have been detected, a novel analysis technique applied to two years of data from the observatory's Large Area Telescope (LAT) has essentially eliminated these particle candidates for the first time.

    WIMPs, or Weakly Interacting Massive Particles, represent a favored class of dark matter candidates. Some WIMPs may mutually annihilate when pairs of them interact, a process expected to produce gamma rays — the most energetic form of light — that the LAT is designed to detect.

    The team examined two years of LAT-detected gamma rays with energies in the range from 200 million to 100 billion electron volts (GeV) from 10 of the roughly two dozen dwarf galaxies known to orbit the Milky Way. Instead of analyzing the results for each galaxy separately, the scientists developed a statistical technique — they call it a "joint likelihood analysis" — that evaluates all of the galaxies at once without merging the data together. No gamma-ray signal consistent with the annihilations expected from four different types of commonly considered WIMP particles was found.

    For the first time, the results show that WIMP candidates within a specific range of masses and interaction rates cannot be dark matter. A paper detailing these results appeared in the Dec. 9, 2011, issue of Physical Review Letters.

  • Gamma rays in the Heart of Cygnus
    2011.11.28
    Located in the vicinity of the second-magnitude star Gamma Cygni, the Cygnus X star-forming region was discovered as a diffuse radio source by surveys in the 1950s. Now, a study using data from NASA's Fermi Gamma-ray Space Telescope finds that the tumult of star birth and death in Cygnus X has managed to corral fast-moving particles called cosmic rays.

    Cosmic rays are subatomic particles — mainly protons — that move through space at nearly the speed of light. In their journey across the galaxy, the particles are deflected by magnetic fields, which scramble their paths and make it impossible to backtrack the particles to their sources. Yet when cosmic rays collide with interstellar gas, they produce gamma rays — the most energetic and penetrating form of light — that travel to us straight from the source.

    The Cygnus X star factory is located about 4,500 light-years away and is believed to contain enough raw material to make two million stars like our sun. Within it are many young star clusters and several sprawling groups of related O- and B-type stars, called OB associations. One, called Cygnus OB2, contains 65 O stars — the most massive, luminous and hottest type — and nearly 500 B stars. These massive stars possess intense outflows that clear out cavities in the region's gas clouds. A tangled web of shockwaves associated with this process impedes the movement of cosmic rays throughout the region. Cosmic rays striking gas nuclei or photons from starlight produce the gamma rays Fermi detects.

    The release on NASA.gov is here.

  • Fermi Discovers Youngest Millisecond Pulsar
    2011.11.03
    An international team of scientists using NASA's Fermi Gamma-ray Space Telescope has discovered a surprisingly powerful millisecond pulsar that challenges existing theories about how these objects form. At the same time, another team has exploited improved analytical techniques to locate nine new gamma-ray pulsars in Fermi data.

    A pulsar, also called a neutron star, is the closest thing to a black hole astronomers can observe directly, crushing half a million times more mass than Earth into a sphere no larger than a city. This matter is so compressed that even a teaspoonful weighs as much as Mount Everest.

    Typically, millisecond pulsars are a billion years or more old, ages commensurate with a stellar lifetime. But in the Nov. 3 issue of Science, the Fermi team reveals a bright, energetic millisecond pulsar only 25 million years old.

    The object, named PSR J1823—3021A, lies within NGC 6624, a spherical assemblage of ancient stars called a globular cluster, one of about 160 similar objects that orbit our galaxy. The cluster is about 10 billion years old and lies about 27,000 light-years away toward the constellation Sagittarius.

    "With this new batch of pulsars, Fermi now has detected more than 100, which is an exciting milestone when you consider that before Fermi's launch only seven of them were known to emit gamma rays," said Pablo Saz Parkinson, an astrophysicist at the Santa Cruz Institute for Particle Physics, University of California Santa Cruz.

  • Fermi Pulsar Interactive Videos
    2011.11.03
    These videos accompany the Fermi Pulsar Interactive here.
  • Fermi's Latest Gamma-ray Census Highlights Cosmic Mysteries
    2011.09.09
    Every three hours, NASA's Fermi Gamma-ray Space Telescope scans the entire sky and deepens its portrait of the high-energy universe. Every year, the satellite's scientists reanalyze all of the data it has collected, exploiting updated analysis methods to tease out new sources. These relatively steady sources are in addition to the numerous transient events Fermi detects, such as gamma-ray bursts in the distant universe and flares from the sun.

    Earlier this year, the Fermi team released its second catalog of sources detected by the satellite's Large Area Telescope (LAT), producing an inventory of 1,873 objects shining with the highest-energy form of light. More than half of these sources are active galaxies whose supermassive black hole centers are causing the gamma-ray emissions.

  • Stellar Odd Couple Makes Striking Flares
    2011.06.29
    Every 3.4 years, pulsar B1259-63 dives twice through the gas disk surrounding the massive blue star it orbits. With each pass, it produces gamma rays. During the most recent event, NASA's Fermi Gamma-ray Space Telescope observed that the pulsar's gamma-ray flare was much more intense the second time it plunged through the disk. Astronomers don't yet know why.

    For the B1259 binary animation, go here.

  • NASA's Fermi Spots 'Superflares' in the Crab Nebula
    2011.05.11
    The famous Crab Nebula supernova remnant has erupted in an enormous flare five times more powerful than any previously seen from the object. The outburst was first detected by NASA's Fermi Gamma-ray Space Telescope on April 12 and lasted six days.

    The nebula, which is the wreckage of an exploded star whose light reached Earth in 1054, is one of the most studied objects in the sky. At the heart of an expanding gas cloud lies what's left of the original star's core, a superdense neutron star that spins 30 times a second. With each rotation, the star swings intense beams of radiation toward Earth, creating the pulsed emission characteristic of spinning neutron stars (also known as pulsars).

    Apart from these pulses, astrophysicists regarded the Crab Nebula to be a virtually constant source of high-energy radiation. But in January, scientists associated with several orbiting observatories — including NASA's Fermi, Swift and Rossi X-ray Timing Explorer — reported long-term brightness changes at X-ray energies.

    Scientists think that the flares occur as the intense magnetic field near the pulsar undergoes sudden restructuring. Such changes can accelerate particles like electrons to velocities near the speed of light. As these high-speed electrons interact with the magnetic field, they emit gamma rays in a process known as synchrotron emission.

    To account for the observed emission, scientists say that the electrons must have energies 100 times greater than can be achieved in any particle accelerator on Earth. This makes them the highest-energy electrons known to be associated with any cosmic source.

    Based on the rise and fall of gamma rays during the April outbursts, scientists estimate that the size of the emitting region must be comparable in size to the solar system. If circular, the region must be smaller than roughly twice Pluto's average distance from the sun.

    For more Crab Nebula media go to #10708.

  • A Flickering X-ray Candle
    2011.01.12
    The Crab Nebula, created by a supernova seen nearly a thousand years ago, is one of the sky's most famous "star wrecks." For decades, most astronomers have regarded it as the steadiest beacon at X-ray energies, but data from orbiting observatories show unexpected variations, showing astronomers their hard X-ray "standard candle" isn't as steady as they once thought. From 1999 to 2008, the Crab brightened and faded by as much as 3.5 percent a year, and since 2008, it has faded by 7 percent. The Gamma-ray Burst Monitor on NASA's Fermi satellite first detected the decline, and Fermi's Large Area Telescope also spotted two gamma-ray flares at even higher energies. Scientists think the X-rays reveal processes deep within the nebula, in a region powered by a rapidly spinning neutron star — the core of the star that blew up. But figuring out exactly where the Crab's X-rays are changing over the long term will require a new generation of X-ray telescopes.
  • Terrestrial Gamma-ray Flashes Create Antimatter
    2011.01.10
    NASA's Fermi Gamma-ray Space Telescope has detected beams of antimatter launched by thunderstorms. Acting like enormous particle accelerators, the storms can emit gamma-ray flashes, called TGFs, and high-energy electrons and positrons. Scientists now think that most TGFs produce particle beams and antimatter.

    For additional animations showing bremsstrahlung and pair production gamma ray reactions, go here.

    For more visualizations showing Fermi's TGF detections, go to#3747, #3748, and #3756.

    For animations of the Fermi spacecraft and matter/antimatter, go to#10707 and #10651.

  • Fermi discovers giant gamma-ray bubbles in the Milky Way
    2010.11.09
    Using data from NASA's Fermi Gamma-ray Space Telescope, scientists have recently discovered a gigantic, mysterious structure in our galaxy. This never-before-seen feature looks like a pair of bubbles extending above and below our galaxy's center.

    But these enormous gamma-ray emitting lobes aren't immediately visible in the Fermi all-sky map. However, by processing the data, a group of scientists was able to bring these unexpected structures into sharp relief.

    Each lobe is 25,000 light-years tall and the whole structure may be only a few million years old. Within the bubbles, extremely energetic electrons are interacting with lower-energy light to create gamma rays, but right now, no one knows the source of these electrons.

    Are the bubbles remnants of a massive burst of star formation? Leftovers from an eruption by the supermassive black hole at our galaxy's center? Or or did these forces work in tandem to produce them? Scientists aren't sure yet, but the more they learn about this amazing structure, the better we'll understand the Milky Way.

    For an animation that shows the inverse Compton scattering responsible for the gamma rays, go to #10690.

    For an animation that shows an artist's interpretation of the Milky Way galaxy and the lobes, go to#10691.

  • Einstein's Cosmic Speed Limit
    2009.10.28
    In its first year of operations, NASA's Fermi Gamma-ray Space Telescope has mapped the entire sky with unprecedented resolution and sensitivity in gamma-rays, the highest-energy form of light. On May 10, 2009 a pair of gamma-ray photons reached Fermi only 900 milliseconds apart after traveling for 7 billion years. Fermi's measurement gives us rare experimental evidence that space-time is smooth as Einstein predicted, and has shut the door on several approaches to gravity where space-time is foamy enough to interfere strongly with light.

    Watch this video on the NASAexplorer YouTube channel.

    For complete transcript, click here.

  • Big Flare
    2015.07.21
    NASA's Fermi satellite sees record flare from a black hole in a galaxy 5 billion light-years away.
  • Two Stars, One Powerful Glow
    2016.10.06
    NASA's Fermi Gamma-ray Space Telescope finds record-breaking binary in a galaxy next door.
  • Gamma-ray Vision
    2016.01.12
    NASA’s Fermi mission provides the best view of the high-energy gamma-ray sky yet seen.
  • Galactic Flare
    2016.01.28
    NASA's Fermi mission detects an outburst of high-energy light from a source more than halfway across the universe.
  • Detecting Superfast Matter
    2013.08.06
    A NASA space telescope pinpoints a source of high-energy cosmic rays.
  • The Gamma-ray Sky
    2014.06.19
    Magnificent bursts of light help scientists pinpoint the most energetic spots in the universe.
  • Cosmic Blast
    2014.09.18
    A stunning amount of energy is unleashed when a star goes nova.
  • Antimatter Explosions
    2012.01.31
    A NASA spacecraft discovers antimatter bursts released by thunderstorms.
  • Galactic Lobes
    2012.03.01
    Gamma rays radiate from the Milky Way's center, but where do they come from?

Spacecraft

  • The GLAST (Fermi) Spacecraft in Orbit
    2007.09.14
    GLAST will be launched into a circular orbit around the Earth at an altitude of about 560 km (350 miles). At that altitude, the observatory will circle Earth every 90 minutes. In sky-survey mode, GLAST will be able to view the entire sky in just two orbits, or about 3 hours. Because gamma rays in the GLAST's energy band are unable to penetrate the Earth's atmostphere, it is essential that GLAST perform its observations from space.
  • 360 Degrees of GLAST
    2007.09.14
    GLAST will carry two instruments: the Large Area Telescope (LAT) and the GLAST Burst Monitor (GBM). The LAT is GLAST's primary instrument and consists of four components: the Tracker, the Calorimeter, the Anticoincidence Detector (ACD), and the Data Acquisition System (DAQ). These instrument components working together will detect gamma rays by using Einstein's famous equation (E=mc(squared) in a technique known as pair production. The GLAST Burst Monitor is a complementary instrument and consists of low-energy detectors, high-energy detectors, and data processing unit. The GBM can see all directions at once, except for the area where Earth blocks its view. When the GBM detects a bright gamma-ray burst, it immediately sends a signal to the LAT to observe that area of the sky.
  • Fermi's LAT Instrument
    2012.02.25
    Fermi's Large Area Telescope (LAT) detects particles produced in a physical process known as pair production that epitomizes Einstein's famous equation, E=mc2. When a gamma ray, which is pure energy (E), slams into a layer of tungsten in one of the tracking towers that compose the LAT, it creates mass (m) in the form of a pair of subatomic particles, an electron and its antimatter counterpart, a positron. Several layers of high-precision silicon detectors track the particles as they move through the instrument. The direction of the incoming gamma ray is determined by projecting the particle paths backward. The particles travel through the trackers until they reach a separate detector called a calorimeter, which absorbs and measures their energies. The LAT produces gamma-ray images of astronomical objects, while also determining the energy of each detected gamma ray.
  • Fermi Collision Avoidance Animations
    2013.04.30
    Animations of the Fermi Gamma-ray Space Telescope and the Cosmos 1805 Tselina-D Soviet satellite from the Fermi Collision Avoidance video.
  • GLAST's New Window on the Universe
    2007.09.14
    The Universe is home to numerous extoic and beautiful phenomena, some of which can generate inconceiveable amounts of energy. GLAST (Gamma-ray Large Area Telescope) will open this high-energy world as the first imaging gamma-ray observatory to survey the entire sky every day and with high sensitivity. Astronomers will gain a superior tool to study how black holes, notorious for pulling matter in, can accelerate jets of gas outward at fantastic speeds. Physicists will be able to search for signals of new fundamental processes that are inaccessable in ground-based accelerators and observatories. And scientists will have a unique opportunity to learn about the every-changing Universe at extreme energies.
  • GLAST Launch and Deployment
    2007.09.14
    GLAST's launch is scheduled for early 2008 from Cape Canaveral Air Station on Florida's eastern coast. GLAST will be carried on a Delta II Heavy launch vehicle, with 9 solid rocket boosters. The solids are actually from the Delta III series (hence the term 'heavy'), mounted on a Delta II. It has a 10-foot fairing and two stages. Stowed in the launch vehicle, the spacecraft is 9.2 feet (2.8 meters) high by 8.2 feet (2.5 meters) in diameter. Once deployed, GLAST becomes a little bit taller and much wider (15 meters) with the Ku-band antenna deployed and the solar arrays extended.
  • Fermi Improves Its Vision For Thunderstorm Gamma-ray Flashes
    2012.12.06
    Thanks to improved data analysis techniques and a new operating mode, the Gamma-ray Burst Monitor (GBM) aboard NASA's Fermi Gamma-ray Space Telescope is now 10 times better at catching the brief outbursts of high-energy light mysteriously produced above thunderstorms.

    The outbursts, known as terrestrial gamma-ray flashes (TGFs), last only a few thousandths of a second, but their gamma rays rank among the highest-energy light that naturally occurs on Earth. The enhanced GBM discovery rate helped scientists show most TGFs also generate a strong burst of radio waves, a finding that will change how scientists study this poorly understood phenomenon.

    Lightning emits a broad range of very low frequency (VLF) radio waves, often heard as pop-and-crackle static when listening to AM radio. The World Wide Lightning Location Network (WWLLN), a research collaboration operated by the University of Washington in Seattle, routinely detects these radio signals and uses them to pinpoint the location of lightning discharges anywhere on the globe to within about 12 miles (20 km).

    Scientists have known for a long time TGFs were linked to strong VLF bursts, but they interpreted these signals as originating from lightning strokes somehow associated with the gamma-ray emission.

    "Instead, we've found when a strong radio burst occurs almost simultaneously with a TGF, the radio emission is coming from the TGF itself," said co-author Michael Briggs, a member of the GBM team.

    The researchers identified much weaker radio bursts that occur up to several thousandths of a second before or after a TGF. They interpret these signals as intracloud lightning strokes related to, but not created by, the gamma-ray flash.

    Scientists suspect TGFs arise from the strong electric fields near the tops of thunderstorms. Under certain conditions, the field becomes strong enough that it drives a high-speed upward avalanche of electrons, which give off gamma rays when they are deflected by air molecules.

    "What's new here is that the same electron avalanche likely responsible for the gamma-ray emission also produces the VLF radio bursts, and this gives us a new window into understanding this phenomenon," said Joseph Dwyer, a physics professor at the Florida Institute of Technology in Melbourne, Fla., and a member of the study team.

    Because the WWLLN radio positions are far more precise than those based on Fermi's orbit, scientists will develop a much clearer picture of where TGFs occur and perhaps which types of thunderstorms tend to produce them.

    Watch this video on YouTube.

  • Fermi Observation of Early Background Light Animation
    2012.11.01
    This animation tracks several gamma rays through space and time, from their emission in the jet of a distant blazar to their arrival in Fermi's Large Area Telescope (LAT). During their journey, the number of randomly moving ultraviolet and optical photons (blue) increases as more and more stars are born in the universe. Eventually, one of the gamma rays encounters a photon of starlight and the gamma ray transforms into an electron and a positron. The remaining gamma-ray photons arrive at Fermi, interact with tungsten plates in the LAT, and produce the electrons and positrons whose paths through the detector allows astronomers to backtrack the gamma rays to their source.

Early Fermi

  • Fermi Launch - June 11, 2008
    2010.12.20
    Footage of the Fermi satellite launch from Cape Canaveral Air Station on June 11, 2008.
  • GLAST Promo Video
    2007.09.17
    NASA's Gamma-ray Large Area Space Telescope (GLAST) is a powerful space observatory that will open a wide window on the universe. Gamma rays are the highest-energy form of light and the gamma-ray sky is spectacularly different from the one we perceive with our own eyes. With a huge leap in all key capabilities, GLAST data will enable scientists to answer persistent questions across a broad range of topics, including supermassive black-hole systems, pulsars, the origina of cosmic rays, and searches for signals new physics. NASA's GLAST mission is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the U.S.
  • GLASTcast Episode 1: What is GLAST?
    2008.05.29
    NASA's GLAST mission is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the U.S.

    The Universe is home to numerous exotic and beautiful phenomena, some of which can generate inconceivable amounts of energy. GLAST will open a new window on this high-energy world. With GLAST, astronomers will have a superior tool to study how black holes, notorious for pulling matter in, can accelerate jets of gas outward at fantastic speeds. Physicists will be able to search for signals of new fundamental processes that are inaccessible in ground-based accelerators and observatories. GLAST's spectacular high-energy gamma-ray "eyeglasses" will reveal hidden wonders, opening our minds to new possibilities and discoveries, expanding our understanding of the Universe and our place in it.

    Interviews with (in order of appearance):

    Steve Ritz - GLAST Project Scientist, NASA Goddard

    Peter Michaelson - Large Area Telescope (LAT) Principal Investigator, Stanford University

    Diego Torres - Large Area Telescope (LAT) Scientist, University of Barcelona

    Neil Gehrels - GLAST Deputy Project Scientist, NASA Goddard

    David Thompson - GLAST Deputy Project Scientist, NASA Goddard

    Luke Drury - Professor of Astronomy, Dublin Institute for Advanced Studies

    Valerie Connaughton - GLAST Burst Monitor (GBM) Team, NASA Marshall/University of Alabama

    Martin Pohl - GLAST Interdisciplinary Scientist, Iowa State University

    Per Carlson - Professor of Elementary Particle Physics, Manne Siegbahn Laboratory

    Charles "Chip" Meegan - GLAST Burst Monitor (GBM) Principal Investigator, NASA Marshall

    Alan Marscher - Professor of Astronomy, Boston University

    Julie McEnery - GLAST Deputy Project Scientist, NASA Goddard

  • GLASTcast Episode 2: What are Gamma Rays?
    2008.05.23
    NASA's GLAST mission is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the U.S.

    Somewhere out in the vast depths of space, a giant star explodes with the power of millions of suns. As the star blows up, a black hole forms at its center. The black hole blows two blowtorches in opposite directions, in narrow jets of gamma rays. NASA's Gamma-ray Large Area Space Telescope, or GLAST, will catch about 200 of these explosions, known as gamma-ray bursts, each year. GLAST's detailed observations may give astronomers the clues they need to unravel the mystery of what exactly produces these gamma-ray bursts, which are the brightest explosions in the universe since the Big Bang.

    Interviews with (in order of appearance):

    Phil Plait - Astronomer, Bad Astronomy

    David Thompson - GLAST Deputy Project Scientist, NASA Goddard

    Valerie Connaughton - GLAST Burst Monitor (GBM) Team, NASA Marshall/University of Alabama

    Neil Gehrels - GLAST Deputy Project Scientist, NASA Goddard

    Isabelle Grenier - Principal Investigator of the GLAST French contribution, French Atomic Energy Commission

    Peter Michaelson - Large Area Telescope (LAT) Principal Investigator, Stanford University

    Charles "Chip" Meegan - GLAST Burst Monitor (GBM) Principal Investigator, NASA Marshall

    Martin Pohl - GLAST Interdisciplinary Scientist, Iowa State University

    Steve Ritz - GLAST Project Scientist, NASA Goddard

  • GLASTCast Episode 3 - Swift and GLAST
    2008.08.05
    NASA's GLAST mission is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the U.S.

    What's the difference between the Swift and GLAST satellites? Both missions look at gamma-ray bursts (GRBs), but in different ways. Swift can rapidly and precisely determine the locations of GRBs and observe their afterglows at X-ray, ultraviolet, and optical wavelengths. GLAST will provide exquisite observations of the burst over the gamma ray spectrum, giving scientists their first complete view of the total energy released in these extraordinary events. Beyond GRB science, GLAST is a multipurpose observatory that will study a broad range of cosmic phenomena. Swift is also a multipurpose observatory, but was built primarily to study GRBs.

    Interviews with (in order of appearance):

    David Thompson - GLAST Deputy Project Scientist, NASA Goddard

    Charles "Chip" Meegan - GLAST Burst Monitor (GBM) Principal Investigator, NASA Marshall

    Lynn Cominsky - GLAST Astrophysicist and Education and Public Outreach Lead, Sonoma State University

    Neil Gehrels - GLAST Deputy Project Scientist, NASA Goddard

    Steve Ritz - GLAST Project Scientist, NASA Goddard

    Alan Marscher - Professor of Astronomy, Boston University

  • GLASTcast Episode 4: Launching a Spacecraft
    2008.08.05
    NASA's GLAST mission is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the U.S.

    The GLAST satellite will launch in 2008 from Cape Canaveral Air Station, on Florida's east coast. GLAST will be carried on a Delta II Heavy launch vehicle, with 9 solid rocket boosters. GLAST is the first imaging gamma-ray observatory to survey the entire sky every day and with high sensitivity. It will give scientists a unique opportunity to learn about the ever-changing Universe at extreme energies.

    Interviews with (in order of appearance):

    Peter Michaelson - Large Area Telescope (LAT) Principal Investigator, Stanford University

    Lynn Cominsky - GLAST Astrophysicist and Education and Public Outreach Lead, Sonoma State University

    David Thompson - GLAST Deputy Project Scientist, NASA Goddard

    Kevin Grady - GLAST Project Manager, NASA Goddard

    Neil Johnson - Large Area Telescope (LAT) Deputy Principal Investigator, US Naval Research Lab

    Jonathan Ormes - Large Area Telescope (LAT) Senior Scientist Advisory Committee, University of Denver

    Charles "Chip" Meegan - GLAST Burst Monitor (GBM) Principal Investigator, NASA Marshall

    Luke Drury - Professor of Astronomy, Dublin Institute for Advanced Studies

    Per Carlson - Professor of Elementary Particle Physics, Manne Siegbahn Laboratory

    Isabelle Grenier - Principal Investigator of the GLAST French contribution, French Atomic Energy Commission

  • GLASTcast Episode 5: Meet the U.S. Team
    2008.08.05
    NASA's GLAST mission is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the U.S.

    This video introduces only a small fraction of the hundreds of U.S. and international GLAST team members. To meet more of the team go to: www.nasa.gov/glast.

    Interviews with (in order of appearance):

    Bill Atwood - GLAST Co-Creator, Santa Cruz Institute of Particle Physics, University of California, Santa Cruz

    David Thompson - GLAST Deputy Project Scientist, NASA Goddard

    Julie McEnery - GLAST Deputy Project Scientist, NASA Goddard

    Steve Ritz - GLAST Project Scientist, NASA Goddard

    Neil Gehrels - GLAST Deputy Project Scientist, NASA Goddard

    Peter Michaelson - Large Area Telescope (LAT) Principal Investigator, Stanford University

    Kevin Grady - GLAST Project Manager, NASA Goddard

    Charles "Chip" Meegan - GLAST Burst Monitor (GBM) Principal Investigator, NASA Marshall

  • GLASTcast Episode 6: 2008 Mission Update
    2008.12.21
    The GLAST mission launched on June 11, 2008 and has been returning remarkable and revolutionary discoveries ever since. Recently renamed to the Fermi Space Telescope, after Nobel Prize winner Enrico Fermi, the mission is expected to discover dozens of new pulsars within its first year alone. The telescope is also giving us new insights into gamma-ray bursts and the massive jets that erupt from distant galaxies. Stay tuned — the mission of NASA's Fermi telescope is just getting started.
  • GLASTcast in HD for Apple TV and iTunes
    2008.08.25
    The Universe is home to numerous exotic and beautiful phenomena, some of which can generate inconceivable amounts of energy. GLAST will open a new window on this high-energy world. With GLAST, astronomers will have a superior tool to study how black holes, notorious for pulling matter in, can accelerate jets of gas outward at fantastic speeds. Physicists will be able to search for signals of new fundamental processes that are inaccessible in ground-based accelerators and observatories. GLAST's spectacular high-energy gamma-ray 'eyeglasses' will reveal hidden wonders, opening our minds to new possibilities and discoveries, expanding our understanding of the Universe and our place in it.
  • GLASTcast for iTunes
    2008.06.03
    The GLAST mission launched on June 11, 2008 and has been returning remarkable and revolutionary discoveries ever since. Recently renamed to the Fermi Space Telescope, after Nobel Prize winner Enrico Fermi, the mission is expected to discover dozens of new pulsars within the first year alone. The telescope is also giving us new insights into gamma-ray bursts and the massive jets that erupt from distant galaxies. Stay tuned — the mission of NASA's Fermi telescope is just getting started.
  • GLAST LAT Integration - B-Roll
    2007.09.17
    In fall of 2006, the LAT was shipped to the General Dynamics facility in Arizona for integration onto the spacecraft bus. The General Dynamics spacecraft bus provides the power, data, and pointing resources that will enable the LAT to perform its survey of the Universe. Subsequent to the mechanical integration, the command, data, and power interfaces between the instrument and the spacecraft were tested rigorously to insure the compatibility of this spaceflight hardware that had been manufactured all around the globe.
  • GLAST LAT Testing - B-Roll
    2007.09.17
    The GLAST LAT (Large Area Telescope) was tested extensively during the summer of 2006 at the U.S. Naval Research Laboratory in Washington, DC. The NRL also contributed to the GLAST project by managing the construction of the LAT Calorimeter.
  • GLAST Prelude, for Brass Quintet, Op.12
    2008.05.31
    NASA's GLAST mission is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institiutions and partners in France, Germany, Italy, Japan, Sweden, and the U.S. Music composed by Nolan Gasser, © 2008 Music performed by the American Brass Quintet
  • GLAST Soundbites
    2008.07.30
    Selected soundbites with Steve Ritz, GLAST Project Scientist; Peter Michelson, LAT Principal Investigator; Charles 'Chip' Meegan, GBM Principal Investigator. NASA's GLAST mission is an astrophysics partnership, developed in collaboration with the U.S. Department of Energy along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the U.S.
  • Highlights of Fermi's First Five Years
    2013.08.21
    This compilation summarizes the wide range of science from the first five years of NASA's Fermi Gamma-ray Space Telescope. Fermi is a NASA observatory designed to reveal the high-energy universe in never-before-seen detail. Launched in 2008, Fermi continues to give astronomers a unique tool for exploring high-energy processes associated with solar flares, spinning neutron stars, outbursts from black holes, exploding stars, supernova remnants and energetic particles to gain insight into how the universe works.

    Fermi detects gamma rays, the most powerful form of light, with energies thousands to billions of times greater than the visible spectrum.

    The mission has discovered pulsars, proved that supernova remnants can accelerate particles to near the speed of light, monitored eruptions of black holes in distant galaxies, and found giant bubbles linked to the central black hole in our own galaxy.

    From blazars to thunderstorms, from dark matter to supernova remnants, catch the highlights of NASA Fermi’s first five years in space.

    View all the Fermi-related media from the last 5 years in the Fermi Gallery.

    For more information about Fermi, visit NASA's Fermi webpage.

  • Fermi All-Sky First Year Progress
    2009.10.28
    This view of the gamma-ray sky constructed from one year of Fermi LAT observations is the best view of the extreme universe to date. The map shows the rate at which the LAT detects gamma rays with energies above 300 million electron volts — about 120 million times the energy of visible light — from different sky directions. Brighter colors equal higher rates.
  • GLAST First Light All Sky Map
    2008.08.26
    NASA's newest observatory, the Gamma-Ray Large Area Space Telescope (GLAST), has begun its mission of exploring the universe in high-energy gamma rays. The spacecraft and its revolutionary instruments passed their orbital checkout with flying colors. NASA announced today that GLAST has been renamed the Fermi Gamma-ray Space Telescope. The new name honors Prof. Enrico Fermi (1901 - 1954), a pioneer in high-energy physics. Scientists expect Fermi will discover many new pulsars in our own galaxy, reveal powerful processes near supermassive black holes at the cores of thousands of active galaxies across, and enable a search for signs of new physical laws.
  • Simulations of the Gamma-Ray Sky
    2007.09.13
    The Gamma-Ray Large Area Space Telescope (GLAST) will observe the sky in gamma-rays with energies between 10 million electron volts (MeV) to 300 billion electron volts (GeV) (a photon of visible light is roughly 2 electron volts). At these energies, the detectors will receive roughly 2 photons every second. At these energies, the objects visible will be active galaxies, quasars, pulsars, and gamma-ray bursts. This visualization is generated from one year of simulated photon event-lists using known sources. These event lists are used for testing the various data analysis software being developed for the project. Due to the extremely low event rate, it takes about one week of event accumulation to see structure in the sky. To generate the 600+ frames of this visualization, the event lists were box-car averaged for a duration of one week for each frame, and each frame shifted 50,000 seconds in time from the previous frame. The low angular resolution of gamma-ray detectors makes point sources appear spread out in the sky. In these maps, the color of each pixel represents the number of photons accumulated in that pixel (over an energy range of 10MeV-300GeV). Horizontally, across the center of the map, is the diffuse emission from the plane of our own Milky Way galaxy. The images are projected in galactic coordinates with a plate carrée projection so there is significant distortion with increasing latitude above the galactic disk. This emission in the galactic plane is created by pulsars and supernova remnants. Located away from this plane is emission from active galaxies and high-velocity pulsars. Occasionally, a bright spot appears which can be a gamma-ray burst or quasar in an active state.

Presentation Resources

  • Fermi TGF Visualization for Science on a Sphere
    2018.05.18
    Visualization of ten years of Fermi observations of Terrestrial Gamma-ray Flashes (TGFs). This version is optimized for display on normal screens, has labels, and dates for each data pass.
  • Fermi Hyperwall--2016 AAS Technical
    2016.01.04
    3x3 hyperwall-resolution animation of the Fermi spacecraft.

    Credit: NASA's Goddard Space Flight Center/CI Lab

  • Fermi Hyperwall--2016 AAS, A Walk Through Fermi Science
    2016.01.04
    For additional Fermi hyperwall visuals please check the second hyperwall page

  • Fermi Hints at Dark Matter
    2014.04.03
    Using public data from NASA's Fermi Gamma-ray Space Telescope, independent scientists at the Fermi National Accelerator Laboratory, Harvard University, MIT and the University of Chicago have developed new maps showing that the galactic center produces more high-energy gamma rays than can be explained by known sources and that this excess emission is consistent with some forms of dark matter.

    No one knows the true nature of dark matter, but WIMPs, or Weakly Interacting Massive Particles, represent a leading class of candidates. Theorists have envisioned a wide range of WIMP types, some of which may either mutually annihilate or produce an intermediate, quickly decaying particle when they collide. Both of these pathways end with the production of gamma rays — the most energetic form of light — at energies within the detection range of Fermi's Large Area Telescope (LAT).

    The galactic center teems with gamma-ray sources, from interacting binary systems and isolated pulsars to supernova remnants and particles colliding with interstellar gas. It's also where astronomers expect to find the galaxy's highest density of dark matter, which only affects normal matter and radiation through its gravity. Large amounts of dark matter attract normal matter, forming a foundation upon which visible structures, like galaxies, are built.

    When the astronomers carefully subtract all known gamma-ray sources from LAT observations of the galactic center, a patch of leftover emission remains. This excess appears most prominent at energies between 1 and 3 billion electron volts (GeV) — roughly a billion times greater than that of visible light — and extends outward at least 5,000 light-years from the galactic center. The researchers find these features difficult to reconcile with other explanations proposed, such as undiscovered pulsars. The gamma-ray spectrum of the excess, its symmetry around the galactic center and its overall brightness, is, however, consistent with annihilations of dark matter particles in the mass range of 31 and 40 GeV.

    The scientists note that discoveries in other astronomical objects, such as dwarf galaxies, and experiments on Earth designed to directly detect dark matter particles will be needed to confirm this interpretation.
    For more information: Fermi Data Tantalize With New Clues To Dark Matter

  • Briefing Materials: NASA Missions Explore Record-Setting Cosmic Blast
    2013.11.21
    On Thursday, Nov. 21, 2013, NASA held a media teleconference to discuss new findings related to a brilliant gamma-ray burst detected on April 27. Audio of the teleconference is available for download here.
  • Fermi's Five-year View of the Gamma-ray Sky
    2013.08.21
    This all-sky view shows how the sky appears at energies greater than 1 billion electron volts (GeV) according to five years of data from NASA's Fermi Gamma-ray Space Telescope. (For comparison, the energy of visible light is between 2 and 3 electron volts.) The image contains 60 months of data from Fermi's Large Area Telescope; for better angular resolution, the map shows only gamma rays converted at the front of the instrument's tracker. Brighter colors indicate brighter gamma-ray sources. The map is shown in galactic coordinates, which places the midplane of our galaxy along the center.

    The five-year Fermi map is available in multiple resolutions below, along with additional plots containing reference information and identifying some of the brightest sources.

  • Fermi Discovers Youngest Millisecond Pulsar
    2011.11.03
    An international team of scientists using NASA's Fermi Gamma-ray Space Telescope has discovered a surprisingly powerful millisecond pulsar that challenges existing theories about how these objects form. At the same time, another team has exploited improved analytical techniques to locate nine new gamma-ray pulsars in Fermi data.

    A pulsar, also called a neutron star, is the closest thing to a black hole astronomers can observe directly, crushing half a million times more mass than Earth into a sphere no larger than a city. This matter is so compressed that even a teaspoonful weighs as much as Mount Everest.

    Typically, millisecond pulsars are a billion years or more old, ages commensurate with a stellar lifetime. But in the Nov. 3 issue of Science, the Fermi team reveals a bright, energetic millisecond pulsar only 25 million years old.

    The object, named PSR J1823—3021A, lies within NGC 6624, a spherical assemblage of ancient stars called a globular cluster, one of about 160 similar objects that orbit our galaxy. The cluster is about 10 billion years old and lies about 27,000 light-years away toward the constellation Sagittarius.

    "With this new batch of pulsars, Fermi now has detected more than 100, which is an exciting milestone when you consider that before Fermi's launch only seven of them were known to emit gamma rays," said Pablo Saz Parkinson, an astrophysicist at the Santa Cruz Institute for Particle Physics, University of California Santa Cruz.

  • Fermi Pulsar Interactive Videos
    2011.11.03
    These videos accompany the Fermi Pulsar Interactive here.
  • Fermi's Latest Gamma-ray Census Highlights Cosmic Mysteries
    2011.09.09
    Every three hours, NASA's Fermi Gamma-ray Space Telescope scans the entire sky and deepens its portrait of the high-energy universe. Every year, the satellite's scientists reanalyze all of the data it has collected, exploiting updated analysis methods to tease out new sources. These relatively steady sources are in addition to the numerous transient events Fermi detects, such as gamma-ray bursts in the distant universe and flares from the sun.

    Earlier this year, the Fermi team released its second catalog of sources detected by the satellite's Large Area Telescope (LAT), producing an inventory of 1,873 objects shining with the highest-energy form of light. More than half of these sources are active galaxies whose supermassive black hole centers are causing the gamma-ray emissions.

  • Fermi discovers giant gamma-ray bubbles in the Milky Way
    2010.11.09
    Using data from NASA's Fermi Gamma-ray Space Telescope, scientists have recently discovered a gigantic, mysterious structure in our galaxy. This never-before-seen feature looks like a pair of bubbles extending above and below our galaxy's center.

    But these enormous gamma-ray emitting lobes aren't immediately visible in the Fermi all-sky map. However, by processing the data, a group of scientists was able to bring these unexpected structures into sharp relief.

    Each lobe is 25,000 light-years tall and the whole structure may be only a few million years old. Within the bubbles, extremely energetic electrons are interacting with lower-energy light to create gamma rays, but right now, no one knows the source of these electrons.

    Are the bubbles remnants of a massive burst of star formation? Leftovers from an eruption by the supermassive black hole at our galaxy's center? Or or did these forces work in tandem to produce them? Scientists aren't sure yet, but the more they learn about this amazing structure, the better we'll understand the Milky Way.

    For an animation that shows the inverse Compton scattering responsible for the gamma rays, go to #10690.

    For an animation that shows an artist's interpretation of the Milky Way galaxy and the lobes, go to#10691.

  • NASM 2015: Our Violent Universe
    2015.11.23
    On September 23, 2015, NASA held a special event at the Smithsonian National Air and Space Museum. “Our Violent Universe” put a spotlight on the latest high energy astrophysics research coming out of NASA, highlighting key missions such as Swift, Fermi, Chandra, NuSTAR, and Hubble. NASA scientists who are leaders in this field gave presentations on some of the most exciting events in our universe, including black holes, supernovae, and gamma ray bursts. NASA does an annual presentation at the Smithsonian National Air and Space Museum to share the latest science from the agency.