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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Watch this video on the NASA Goddard YouTube channel.
Complete transcript available.
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.
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.
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.
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.
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.
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.
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.
"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.
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.
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.
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.
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.
For the B1259 binary animation, go here.
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.
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.
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.
Watch this video on the NASAexplorer YouTube channel.
For complete transcript, click here.
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.
Music:
The Success by Keys of Moon | https://soundcloud.com/keysofmoon
Music promoted by https://www.free-stock-music.com
Creative Commons Attribution 3.0 Unported License
https://creativecommons.org/licenses/by/3.0/deed.en_US
Watch this video on the NASA Goddard YouTube channel.
Complete transcript available.
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
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
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
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
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
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.
Credit: NASA's Goddard Space Flight Center/CI Lab
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
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.
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.
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.
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.