The Fermi Gamma-ray Space Telescope (FGST, also FGRST), formerly called the Gamma-ray Large Area Space Telescope (GLAST), is a space observatory being used to perform gamma-ray astronomy observations from low Earth orbit. Its main instrument is the Large Area Telescope (LAT), with which astronomers mostly intend to perform an all-sky survey studying astrophysical and cosmological phenomena such as active galactic nuclei, pulsars, other high-energy sources and dark matter. Another instrument aboard Fermi, the Gamma-ray Burst Monitor (GBM; formerly GLAST Burst Monitor), is being used to study gamma-ray bursts and solar flares.
Fermi, named for high-energy physics pioneer Enrico Fermi, was launched on 11 June 2008 aboard a Delta II 7920-H rocket. The mission is a joint venture of NASA, the United States Department of Energy, and government agencies in France, Germany, Italy, Japan, and Sweden, becoming the most sensitive gamma-ray telescope on orbit, succeeding INTEGRAL. The project is a recognized CERN experiment (RE7).
The entire gamma-ray sky is unwrapped into a rectangular map, with the center of our Milky Way galaxy located in the middle, in this 14-year time-lapse of the gamma-ray sky. A moving source, our Sun, can be seen following a curving path through the sky, a reflection of Earth’s annual orbital motion. Watch for strong flares that occasionally brighten the Sun.
The central plane of our galaxy is on full display, glowing in gamma rays produced when accelerated particles (cosmic rays) interact with interstellar gas and starlight. Pulsars and supernova remnants, all bright gamma-ray sources for Fermi, also fleck the Milky Way band. Above and below the bright central plane, where our view of the broader cosmos becomes clearer, splotches of color brighten and fade. These sources are jets of particles moving at nearly the speed of light driven by supermassive black holes in distant galaxies. The jets happen to point almost directly toward Earth, which enhances their brightness and variability. Over a few days, these galaxies can erupt to become some of the brighest objects in the gamma-ray sky and then fade to obscurity.
In these maps, brighter colors indicate greater numbers of gamma rays detected by Fermi’s Large Area Telescope from Aug. 10, 2008, to Aug. 2, 2022.
Video credit: NASA’s Goddard Space Flight Center
The entire gamma-ray sky is shown as two circular views centered on the north (left) and south poles of our Milky Way galaxy in this 14-year time-lapse of the gamma-ray sky. The central plane of our galaxy wraps around the edges of both circles, suppressing its glow and improving the view of black-hole-powered galaxies in the distant universe. Their gamma rays come from jets produced by supermassive black holes in distant galaxies that point almost directly toward Earth, which enhances their brightness and variability. Over a few days, these galaxies can erupt to become some of the brighest objects in the gamma-ray sky and then fade to obscurity. A moving source, our Sun, can be seen arcing up and down the circles as it appears to move through the sky, a reflection of Earth’s annual orbital motion. Watch for strong flares that occasionally brighten the Sun. In these maps, brighter colors indicate greater numbers of gamma rays detected by Fermi’s Large Area Telescope from Aug. 10, 2008, to Aug. 2, 2022.
A new study of observations from NASA’s Fermi Gamma-ray Space Telescope has discovered a faint but sprawling glow around a nearby pulsar. If visible to the human eye, this gamma-ray halo would appear larger in the sky than the famed Big Dipper star pattern. The halo suggests this same pulsar could be responsible for a decade-long puzzle about one type of cosmic particle arriving from beyond the solar system that is unusually abundant near Earth — positrons, the antimatter version of electrons.
A neutron star is the crushed core left behind when a star much more massive than the Sun runs out of fuel, collapses under its own weight and explodes as a supernova. We see some neutron stars as pulsars, rapidly spinning objects emitting beams of radio waves, light, X-rays and gamma rays that, much like a lighthouse, regularly sweep across our line of sight from Earth.
Geminga (pronounced geh-MING-a) is among the brightest pulsars at gamma-ray energies. To study its halo, scientists had to subtract out all other sources of gamma rays, including diffuse light produced by cosmic ray collisions with interstellar gas clouds. Ten different models of interstellar emission were evaluated. What remained when these sources were removed was a vast, oblong glow spanning some 20 degrees — about 40 times the apparent size of a full Moon — at an energy of 10 billion electron volts (GeV), and even larger at lower energies.
The team determined that Geminga alone could be responsible for as much as 20% of the high-energy positrons seen by other space experiments. Extrapolating this to the cumulative emission of positrons from all pulsars in our galaxy, the scientists say it’s clear that pulsars remain the best explanation for the observed excess of positrons.
Video credit: NASA’s Goddard Space Flight Center/Scott Wiessinger (USRA): Producer/Francis Reddy (University of Maryland College Park): Science writer/Mattia Di Mauro (Catholic University of America): Visualizer/Mattia Di Mauro (Catholic University of America): Scientist
Astronomers using NASA’s Fermi Gamma-ray Space Space Telescope and the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) have found a pulsar hurtling through space at nearly 2.5 million miles an hour — so fast it could travel the distance between Earth and the Moon in just 6 minutes.
Pulsars are superdense, rapidly spinning neutron stars left behind when a massive star explodes. This one, dubbed PSR J0002+6216 (J0002 for short), sports a radio-emitting tail pointing directly toward the expanding debris from a recent supernova explosion. Thanks to its narrow dart-like tail and a fortuitous viewing angle, astronomers can trace this pulsar straight back to its birthplace. Further study of J0002 will help us better understand how these explosions are able to ‘kick’ neutron stars to such high speed.
The pulsar is located about 6,500 light-years away in the constellation Cassiopeia. It was discovered in 2017 by a citizen-science project called Einstein@Home , which uses downtime on the computers of volunteers to process Fermi gamma-ray data and has identified 23 gamma-ray pulsars to date. J0002 spins 8.7 times a second, producing a pulse of gamma rays with each rotation, and has about 1.5 times the mass of the Sun. The pulsar lies about 53 light-years from the center of a supernova remnant called CTB 1. Its rapid motion through interstellar gas results in shock waves that produce the tail of magnetic energy and accelerated particles detected at radio wavelengths using the VLA. The tail extends 13 light-years and clearly points back to the center of CTB 1.
Using Fermi data and a technique called pulsar timing, the team was able to measure how quickly and in what direction the pulsar was moving across our line of sight thanks to Fermi’s 10-year data covering the entire sky. J0002 is speeding through space five times faster than the average pulsar and faster than 99 percent of those with measured speeds. It will eventually escape our galaxy.
Francis Reddy (University of Maryland College Park): Lead Science Writer
Scott Wiessinger (USRA): Lead Producer
Jeanette Kazmierczak (University of Maryland College Park): Science Writer
Music credit: “Forensic Scientist” from Killer Tracks
“About a year ago, astronomers excitedly reported the first detection of electromagnetic waves, or light, from a gravitational wave source. Now, a year later, researchers are announcing the existence of a cosmic relative to that historic event. The discovery was made using data from telescopes including NASA’s Chandra X-ray Observatory, Fermi Gamma-ray Space Telescope, Neil Gehrels Swift Observatory, the NASA/ESA Hubble Space Telescope, and the Discovery Channel Telescope (DCT).
The object of the new study, called GRB150101B, was first reported as a gamma-ray burst detected by Fermi in January 2015. This detection and follow-up observations at other wavelengths show GRB150101B shares remarkable similarities to the neutron star merger and gravitational wave source discovered by Advanced Laser Interferometer Gravitational Wave Observatory (LIGO) and its European counterpart Virgo in 2017 known as GW170817. The latest study concludes that these two separate objects may, in fact, be related.”
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