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. ||

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. ||

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. ||

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. ||

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.Watch this video on YouTube. ||

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.Watch this video on YouTube. ||

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. ||

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. ||

Explore how gamma-ray telescopes in space and on Earth captured an outburst of high-energy light from PKS 1441+25, a black-hole-powered galaxy more than halfway across the universe.Credit: NASA's Goddard Space Flight CenterWatch this video on the NASA Goddard YouTube channel.For complete transcript, click here. || PKS_1441_still_1.png (1920x1080) [2.1 MB] || PKS_1441_still_1_print.jpg (1024x576) [45.3 KB] || PKS_1441_still_1_searchweb.png (320x180) [57.1 KB] || PKS_1441_still_1_thm.png (80x40) [7.6 KB] || PKS_1441_ProRes_1920x1080_2997.mov (1920x1080) [2.8 GB] || PKS_1441_H264_Best_1920x1080_2997.mov (1920x1080) [1.5 GB] || PKS_1441_H264_Good_1920x1080_2997.mov (1920x1080) [244.3 MB] || PKS_1441_Blazar_FINAL_youtube_hq.mov (1920x1080) [947.0 MB] || PKS_1441_1920x1080_4mbps.mp4 (1920x1080) [105.6 MB] || PKS_1441_Blazar_FINAL_appletv.m4v (1280x720) [126.1 MB] || PKS_1441_Blazar_FINAL_appletv.webm (1280x720) [26.3 MB] || PKS_1441_Blazar_FINAL_appletv_subtitles.m4v (1280x720) [126.2 MB] || PKS_1441_SRT_captions.en_US.srt [4.5 KB] || PKS_1441_SRT_captions.en_US.vtt [4.5 KB] || NASA_PODCAST_PKS_1441_Blazar_FINAL_ipod_sm.mp4 (320x240) [43.8 MB] ||

Tour the best view of the high-energy gamma-ray sky yet seen. This video highlights the plane of our galaxy and identifies objects producing gamma rays with energies greater than 1 TeV. Watch this video on the NASA Goddard YouTube channel.For complete transcript, click here.Credit: NASA's Goddard Space Flight Center || 2FHL_Still_print.jpg (1024x576) [66.4 KB] || 2FHL_Still.png (3840x2160) [19.0 MB] || 2FHL_Still_searchweb.png (320x180) [55.9 KB] || 2FHL_Still_thm.png (80x40) [5.5 KB] || 12019_2FHL_H264_Good_1920x1080_2997.mov (1920x1080) [39.6 MB] || 12019_2FHL_H264_Good_1920x1080_2997.webm (1920x1080) [9.9 MB] || 12019_2FHL_3840x2160_FINAL_appletv.m4v (1280x720) [49.2 MB] || 12019_2FHL_3840x2160_FINAL_appletv_subtitles.m4v (1280x720) [49.3 MB] || 12019_2FHL_SRT_Captions.en_US.srt [330 bytes] || 12019_2FHL_SRT_Captions.en_US.vtt [343 bytes] || 12019_2FHL_3840x2160_2997_20mbps.mp4 (3840x2160) [190.4 MB] || 12019_2FHL_3840x2160_2997_40mbps.mp4 (3840x2160) [371.2 MB] || 12019_2FHL_3840x2160_FINAL_lowres.mp4 (480x272) [13.0 MB] || NASA_PODCAST_12019_2FHL_3840x2160_FINAL_ipod_sm.mp4 (320x240) [17.8 MB] || 12019_2FHL_ProRes_3840x2160_2997.mov (3840x2160) [3.8 GB] ||