Tracing the History of Starlight with NASA's Fermi Mission
Scientists using data from NASA's Fermi Gamma-ray Space Telescope have measured all the starlight produced over 90 percent of the universe's history. The analysis, which examines the gamma-ray output of distant galaxies, estimates the formation rate of stars and provides a reference for future missions that will explore the still-murky early days of stellar evolution.
One of the main goals of the Fermi mission is to assess the extragalactic background light (EBL), a cosmic fog composed of all the ultraviolet, visible and infrared light stars have created over the universe's history. Because starlight continues to travel across the cosmos long after its sources have burned out, measuring the EBL allows astronomers to study stellar formation and evolution separately from the stars themselves.
The collision between a high-energy gamma ray and infrared light transforms the energy into a pair of particles, an electron and its antimatter counterpart, a positron. The same process occurs when medium-energy gamma rays interact with visible light, and low-energy gamma rays interact with ultraviolet light. Enough of these interactions occur over cosmic distances that the farther back scientists look, the more evident their effects become on gamma-ray sources, enabling a deep probe of the universe's stellar content.
The scientists examined gamma-ray signals from 739 blazars -- galaxies with monster black holes at their centers -- collected over nine years by Fermi's Large Area Telescope (LAT). The measurement quintuples the number of blazars used in an earlier Fermi EBL analysis published in 2012 and includes new calculations of how the EBL builds over time, revealing the peak of star formation around 10 billion years ago.
Music: "Inducing Waves" from Killer Tracks
Credit: NASA's Goddard Space Flight Center
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Read more: https://www.nasa.gov/feature/goddard/2018/nasa-s-fermi-traces-the-history-of-starlight-across-cosmos
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Fermi Space Telescope Links Cosmic Neutrino to Monster Black Hole
For the first time ever, scientists using 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.
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.
Light Years Away
Fermi's Gamma-Ray Burst Monitor
The Gamma-ray Burst Monitor (GBM) is one of the instruments aboard the Fermi Gamma-ray Space Telescope. The GBM studies gamma-ray bursts, the most powerful explosions in the universe, as well as other flashes of gamma rays. Gamma-ray bursts are created when massive stars collapse into black holes or when two superdense stars merge, also producing a black hole. The GBM sees these bursts across the entire sky, and scientists are using its observations to learn more about the universe.
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Public Lecture | 10 Years of Cosmic Fireworks with the Fermi Gamma-ray Space Telescope
A single gamma ray carries millions of times the energy of a single photon of visible light. This means that gamma rays are produced only in the most convulsive environments in the universe – pulsars spinning inside huge magnetic fields, stars in binary systems devouring their partners, and black holes at the centers of galaxies swallowing gas clouds more massive than our sun. The Fermi Gamma-ray Space Telescope was launched on June 11, 2008, to measure these extreme astronomical events. In this lecture, SLAC scientist Eric Charles describes how we observe astronomical gamma rays and why we must go to space to see them. Then he discusses how 10 years of observations from the Fermi Telescope have changed our understanding of the most violent objects in the universe.
About the Speaker:
Eric Charles grew up in New Mexico. He received his PhD in high-energy particle physics from the University of Wisconsin in 2002. After three years as a postdoctoral fellow at Lawrence Berkeley National Lab, he moved to SLAC in 2005 to help with the construction and testing of the Fermi Gamma-ray Space Telescope, and stayed on as a member of the Fermi instrument team. He’s been working to improve the performance of the telescope and actively studying the data it gathers on the gamma-ray sky. His hobbies include metal-working and pyrotechnics.
Fermi Gamma-ray Space Telescope: 10 Years of Discoveries
On June 11, 2018, NASA’s Fermi Gamma-ray Space Telescope celebrated 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.
Credit: NASA’s Goddard Space Flight Center
Scott Wiessinger (USRA): Lead Producer
Jeanette Kazmierczak (University of Maryland College Park): Lead Science Writer
Julie McEnery (NASA/GSFC): Narrator
Francis Reddy (University of Maryland College Park): Science Writer
Chris Meaney (KBRwyle): Animator
Walt Feimer (KBRwyle): Animator
Scott Wiessinger (USRA): Animator
Music: "Unseen Husband" from Killer Tracks
Fermi Bubbles: Our Galaxy's Giant Gamma Ray Mystery
Fermi bubbles are made up of gamma rays, but where they came from is still up for debate. Did they come from a star-forming region, or the black hole at the middle of our galaxy?
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Sources:
https://arstechnica.com/science/2013/01/star-formation-drives-huge-bubbles-in-the-milky-way/
https://www.nasa.gov/mission_pages/GLAST/news/new-structure.html
https://news.nationalgeographic.com/news/2010/03/100303-gamma-ray-fog-fermi-dragons/
https://arstechnica.com/science/2017/09/highest-energy-cosmic-rays-bounce-off-bubble-irradiate-earth/
http://www.skyandtelescope.com/astronomy-resources/understanding-fermi-bubbles/
http://astronomy.com/news/2017/03/fermi-bubbles
http://hubblesite.org/news_release/news/2017-10
Images:
https://svs.gsfc.nasa.gov/12313
https://www.nasa.gov/mission_pages/GLAST/news/new-structure.html
https://svs.gsfc.nasa.gov/20142
https://svs.gsfc.nasa.gov/30682
https://svs.gsfc.nasa.gov/30796
An Ordinary Gamma-ray Burst with Extraordinary Consequences
On Aug. 17, the Gamma-ray Burst Monitor on NASA's Fermi Gamma-ray Space Telescope saw a short burst of gamma rays a smashup of neutron stars, marking the first-ever detection of light from a gravitational wave source. NASA scientists Colleen Wilson-Hodge and Tyson Littenberg explain what happened and what it means for science and discovery.
Fermi Detects Gamma-ray Puzzle from M31
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.
NASA's Fermi telescope has detected a gamma-ray excess at the center of the Andromeda galaxy that's similar to a signature Fermi previously detected at the center of our own Milky Way. Watch to learn more.
Credit: NASA's Goddard Space Flight Center/Scott Wiessinger
Music: "Lost Time" from Killer Tracks
For more information: https://www.nasa.gov/feature/goddard/2017/nasas-fermi-finds-possible-dark-matter-ties-in-andromeda-galaxy
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NASA's Fermi space telescope detected new solar flares
NASA's Fermi Gamma-ray Space Telescope can now detect solar flares occuring on the side of the sun it cannot see. This could help scientists better understand solar storms and improve forecasts for future outbursts.
Video courtesy of NASA
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NASA's Fermi Mission / Fermi Gamma-ray Space Telescope | UPSC Current Affairs Prelims 2017
Most Important UPSC Current Affairs for Prelims 2017 - Fermi Mission / Fermi Gamma-ray Space Telescope
NASA's Fermi Finds the Farthest Blazars
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 Fermis 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 LATs 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.
NASAs Fermi Gamma-ray Space Telescope has discovered the five most distant gamma-ray blazars yet known. The light detected by Fermi left these galaxies by the time the universe was two billion years old. Two of these galaxies harbor billion-solar-mass black holes that challenge current ideas about how quickly such monsters could grow.
Credit: NASA’s Goddard Space Flight Center/Scott Wiessinger
Read more: https://www.nasa.gov/feature/goddard/2017/nasas-fermi-discovers-the-most-extreme-blazars-yet
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Fermi Sees Gamma Rays from Far Side Solar Flares
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 NASAs 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 as 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.
Credit: NASA’s Goddard Space Flight Center/Scott Wiessenger
Music: "Jupiters Eye" from Killer Tracks
Read more: https://www.nasa.gov/feature/goddard/2017/nasas-fermi-sees-gamma-rays-from-hidden-solar-flares/
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Dramatically Sharper Gamma-ray Telescope Spots Energetic Sites | Video
A software upgrade on the ground to analyze data retrieved from NASA's Fermi Gamma-ray Space Telescope's Large Area Telescope (LAT) has increased quality by 40 percent. The NASA Fermi team says it "effectively sharpens the LAT's view while also significantly widening its useful energy range. -- Full Story: http://goo.gl/EPRBwV
Credit: NASA/GSFC
NASA | Best-Ever View of the High-Energy Gamma-ray Sky - 4K
This image, constructed from more than six years of observations by NASA's Fermi Gamma-ray Space Telescope, is the first to show how the entire sky appears at energies between 50 billion (GeV) and 2 trillion electron volts (TeV).
A diffuse glow fills the sky and is brightest in the middle of the map, along the central plane of our galaxy. The famous Fermi Bubbles, first detected in 2010, appear as red extensions north and south of the galactic center and are much more pronounced at these energies. Discrete gamma-ray sources include pulsar wind nebulae and supernova remnants within our galaxy, as well as distant galaxies called blazars powered by supermassive black holes. Labels show the highest-energy sources, all located within our galaxy and emitting gamma rays exceeding 1 TeV.
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. This 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. The improved data, known as Pass 8, effectively sharpens the Large Area Telescope's (LAT) 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 cataloged 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.
Read more: http://www.nasa.gov/feature/goddard/2016/nasas-fermi-space-telescope-sharpens-its-high-energy-vision
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NASA | Fermi Detects First Gamma-ray Pulsar in Another Galaxy
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.
Read more at http://www.nasa.gov/feature/goddard/nasas-fermi-satellite-detects-first-gamma-ray-pulsar-in-another-galaxy
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Gamma Ray Bursts and Recent Results from the Fermi Mission - Peter Michelson (SETI Talks)
Dr. Michelson is the Principal Investigator of the Large Area Telescope on the Fermi Observatory.
The Large Area Telescope (LAT) on the Fermi Observatory scans the entire sky once every three hours. It has revealed many types of high-energy sources including gamma-ray bursts, many types of pulsars, active galaxies, and binary systems.
In this talk Dr. Michelson will give an overview of Fermi’s discoveries and offer speculation of what might be found next, including possible sources of gravitational radiation.
Fermi Gamma Ray Rain
This visualization shows gamma rays detected during 3C 279's big flare by the LAT instrument on NASA's Fermi satellite. The flare is an abrupt shower of "rain" that trails off toward the end of the movie. Gamma rays are represented as expanding circles reminiscent of raindrops on water. Both the maximum size of the circle and its color represent the energy of the gamma ray, with white lowest and magenta highest. The highest-energy gamma ray the LAT detected during this flare, 52 billion electron volts, arrives near the end. In a second version of the visualization, a background map shows how the LAT detects 3C 279 and other sources by accumulating high-energy photons over time (brighter squares reflect higher numbers of gamma rays). The movie starts on June 14 and ends June 17. The area shown is a region of the sky five degrees on a side and centered on the position of 3C 279.
Credit: NASA/DOE/Fermi LAT Collaboration
NASA | Gamma-Ray "Raindrops" From Flaring Blazar
This visualization shows gamma rays detected during 3C 279's big flare by the LAT instrument on NASA's Fermi satellite. The flare is an abrupt shower of "rain" that trails off toward the end of the movie. Gamma rays are represented as expanding circles reminiscent of raindrops on water. Both the maximum size of the circle and its color represent the energy of the gamma ray, with white lowest and magenta highest. The highest-energy gamma ray the LAT detected during this flare, 52 billion electron volts, arrives near the end. In a second version of the visualization, a background map shows how the LAT detects 3C 279 and other sources by accumulating high-energy photons over time (brighter squares reflect higher numbers of gamma rays). The movie starts on June 14 and ends June 17. The area shown is a region of the sky five degrees on a side and centered on the position of 3C 279.
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.
Read more at: http://www.nasa.gov/feature/goddard/nasas-fermi-sees-record-flare-from-a-black-hole-in-a-distant-galaxy
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Pulsar's Dramatic Morph Caught by Space Telescope | Video
NASA Fermi Gamma-ray Space Telescope detected a never-before-seen change in a binary star system in the constellation Sextants. The pulsar ceased its radio 'beacon' but started bright gamma ray emissions. This animation explains the behavior.
Credit: NASA/GSFC
Five Illuminating Years From The Fermi Gamma-ray Space Telescope | Video
Launched in 2008, NASA's Fermi Gamma-ray Space Telescope has given scientists the ability to explore high-energy processes associated with a number of cosmic phenomena: black holes, solar flares, rapidly spinning neutron stars, & super nova remnants.
SLAC All Access: Fermi Gamma-ray Space Telescope
Three hundred and fifty miles overhead, the Fermi Gamma-ray Space Telescope silently glides through space. From this serene vantage point, the satellite's instruments watch the fiercest processes in the universe unfold. Pulsars spin up to 700 times a second, sweeping powerful beams of gamma-ray light through the cosmos. The hyperactive cores of distant galaxies spew bright jets of plasma. Far beyond, something mysterious explodes with unfathomable power, sending energy waves crashing through the universe.
Stanford professor and KIPAC member Roger W. Romani talks about this orbiting telescope, the most advanced ever to view the sky in gamma rays, a form of light at the highest end of the energy spectrum that's created in the hottest regions of the universe.
For more information, visit:
http://fgst.slac.stanford.edu/
Record Breaking Gamma-Ray Burst Captured By Fermi | Video
A record breaking Gamma-ray burst captured by NASA's Fermi Gamma-ray Telescope is depicted in the first animation as the comparatively bright spot in the sky and in the second more detailed animation showing only a 20-degree-wide region of the sky.
NASA | What is Fermi?
The Fermi Gamma-ray Space Telescope is a NASA observatory designed to reveal the high-energy universe in never-before-seen detail. With Fermi, astronomers have a unique tool to explore 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. How powerful? The energy of visible light falls between 2 and 3 electron volts, but the gamma rays detected by Fermi have energies several thousand to billions of times greater.
Fermi carries two instruments. Its Large Area Telescope (LAT) is vastly more capable than instruments flown previously, with higher angular resolution, wider field of view, greater energy resolution and range, and more precise time resolution for each gamma ray detected. The LAT tracks gamma rays with energies from 20 million electron volts (MeV) to more than 300 billion electron volts (GeV).
Fermi makes one orbit around Earth every 96 minutes and points the LAT upward at all times so our home planet never blocks its view of the cosmos. 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, which allows the LAT to cover the entire sky in just two orbits. (For a LAT's-eye view of these motions, see this http://www.youtube.com/watch?v=_QpMeEdmZPM).
Every few weeks, the LAT deviates from its normal 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.
Fermi's secondary instrument, the Gamma-ray Burst Monitor (GBM) has a much larger field of view, covering the entire sky not blocked by Earth. The GBM provides spectral coverage from the lower limit of the LAT down to 8,000 electron volts. The GBM is now the premier detector of gamma-ray bursts and has provided new insight into terrestrial gamma-ray flashes, high-energy bursts produced above thunderstorms.
With the LAT and GBM, Fermi is a flexible observatory for investigating the great range of astrophysical phenomena best studied in high-energy gamma rays. Since its launch on June 11, 2008, Fermi has made many discoveries. Some of these findings include:
Testing the fabric of time and space: http://www.youtube.com/watch?v=1mkKhn53L68
Gigantic gamma-ray emitting bubbles in the Milky Way: http://www.youtube.com/watch?v=sXmPxSP225Y
Antimatter from lightning on Earth: http://www.youtube.com/watch?v=lXKt7UVjd-I
Huge flares in the Crab Nebula: http://www.youtube.com/watch?v=qDhdwgK218E
A surprisingly young millisecond pulsar: http://www.youtube.com/watch?v=eZL-xynHopo
New insights into dark matter: http://www.youtube.com/watch?v=i5ucytz2C7I
Gamma rays from solar flares: http://www.youtube.com/watch?v=mc-wQwaUh_Q
Light from the early universe: http://www.youtube.com/watch?v=L51cqVTv37I
Proving supernova remnants produce cosmic rays: http://www.youtube.com/watch?v=C3ue7cEocvI
For more information about Fermi: http://www.nasa.gov/mission_pages/GLAST/main/index.html
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NASA | Fermi Traces a Celestial Spirograph
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.
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NASA | Fermi Proves Supernova Remnants Produce Cosmic Rays
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.
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Space Fan News #93: The Fermi Gamma Ray Observatory
The Fermi Gamma Ray Observatory is out there, collecting gamma rays on photon at a time, so you don't have to!
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Earth Gamma Ray Blasters
From NASA Goddard Space Flight Center. NASA's Fermi Gamma-ray Space Telescope has been catching brief outbursts of high-energy light that are 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), researchers routinely detect these radio signals and use them to pinpoint the location of lightning discharges anywhere on the globe to within about 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.
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.
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.
The GBM scientists predict the new operating mode and analysis techniques will allow them to catch about 850 TGFs each year. While this is a great improvement, it remains a small fraction of the roughly 1,100 TGFs that fire up each day somewhere on Earth, according to the team's latest estimates.
How Gamma-Ray Pulsars Are Detected | Video
The large area detector (LAT) onboard the Fermi Gamma-Ray Space Telescope records the arrival times and direction of gamma photons. By analyzing this data, scientists can pinpoint these rotating neutron stars through photon count patterns.
Mysterious Gamma-Ray Objects Baffle Astronomers | Video
The Fermi Gamma-Ray Telescope detected almost 500 sources of gamma ray emitting objects in its field of view. But the sources for more then 30% of them are completely unknown. Black holes and neutron stars emit gamma-radiation.
NASA's Fermi Telescope Finds Youngest Millisecond Pulsar
The Fermi Gamma-ray Space Telescope has discovered the youngest known millisecond gamma-ray pulsar in an old globular cluster of stars. A pulsar is a type of neutron star that emits electromagnetic energy at periodic intervals; a millisecond pulsar does soe every one- to ten-milliseconds, or one one-thousandth of a second.. A neutron star is the closest thing to a black hole that 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. Recent discoveries of more gamma-ray pulsars have pushed their number past 100.
ScienceCasts: 600 Mysteries in the Night Sky
Visit http://science.nasa.gov/science-news/science-at-nasa/2011/18oct_600mysteries/ for the full story.
The Fermi Gamma-ray Space Telescope recently produced a map of the night sky. Out of 1873 new sources, nearly 600 were complete mysteries. In this week's ScienceCast, researchers speculate on the nature of the mystery objects - including the possibility that they are made of dark matter.
Gamma-Ray Scope Reveal 'Blazars' A-Plenty
The Fermi Space Telescope detectors often spots supermassive black holes whose polar jets are pointed in our direction. These active galactic nuclei appear as bright gamma ray emissions. About a 1000 of these powerful objects have been detected.
Gamma Ray Thunderstorms
A big surprise from the Fermi Gamma Ray Space Telescope. It detected beams of antimatter produced above thunderstorms on Earth, a phenomenon never seen before.
Scientists think the antimatter particles were formed in a terrestrial gamma-ray flash (TGF), a brief burst produced inside thunderstorms and shown to be associated with lightning. It is estimated that about 500 TGFs occur daily worldwide, but most go undetected.
"These signals are the first direct evidence that thunderstorms make antimatter particle beams," said Michael Briggs, a member of Fermi's Gamma-ray Burst Monitor (GBM) team at the University of Alabama in Huntsville (UAH).
Fermi is designed to monitor gamma rays, the highest energy form of light. When antimatter striking Fermi collides with a particle of normal matter, both particles immediately are annihilated and transformed into gamma rays. The GBM has detected gamma rays with energies of 511,000 electron volts, a signal indicating an electron has met its antimatter counterpart, a positron.
Although Fermi's GBM is designed to observe high-energy events in the universe, it's also providing valuable insights into this strange phenomenon. The GBM constantly monitors the entire celestial sky above and the Earth below. The GBM team has identified 130 TGFs since Fermi's launch in 2008.
The spacecraft was located immediately above a thunderstorm for most of the observed TGFs, but in four cases, storms were far from Fermi. In addition, lightning-generated radio signals detected by a global monitoring network indicated the only lightning at the time was hundreds or more miles away. During one TGF, which occurred on Dec. 14, 2009, Fermi was located over Egypt. But the active storm was in Zambia, some 2,800 miles to the south. The distant storm was below Fermi's horizon, so any gamma rays it produced could not have been detected.
"Even though Fermi couldn't see the storm, the spacecraft nevertheless was magnetically connected to it," said Joseph Dwyer at the Florida Institute of Technology in Melbourne, Fla. "The TGF produced high-speed electrons and positrons, which then rode up Earth's magnetic field to strike the spacecraft."
The beam continued past Fermi, reached a location, known as a mirror point, where its motion was reversed, and then hit the spacecraft a second time just 23 milliseconds later. Each time, positrons in the beam collided with electrons in the spacecraft. The particles annihilated each other, emitting gamma rays detected by Fermi's GBM.
NASA | Fermi discovers giant gamma-ray bubbles in the Milky Way
Using data from NASA's Fermi Gamma-ray Space Telescope, scientists have 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. 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.
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Fermi Gamma Ray Observations - Stefan Funk (SETI Talks)
SETI Talks Archive: http://seti.org/talks
The Fermi Gamma-ray Space Telescope, formerly called GLAST, is a satellite mission designed to measure gamma-rays in the energy range 20 MeV to greater than 300 GeV, with supporting measurements for gamma-ray bursts from 8 keV to 30 MeV. In addition to breakthrough capabilities in energy coverage and localization, the very large field of view enables observations of 20% of the sky at any instant, and the entire sky on a timescale of a few hours. With its recent launch on 11 June 2008, Fermi now opens a new and important window on a wide variety of phenomena, including pulsars, black holes and active galactic nuclei, gamma-ray bursts, the origin of cosmic rays and supernova remnants, and searches for hypothetical new phenomena such as supersymmetric dark matter annihilations. Dr. Funk will discuss early results and science opportunities of investigations of the Universe with high-energy eyes.