A new movie from NASA’s Fermi mission shows the intensity of gamma rays — the highest-energy form of light — with energies above 200 million electron volts (MeV) detected by Fermi’s Large Area Telescope between August 2008 and August 2022. For comparison, visible light has energies between 2 and 3 electron volts. Brighter colors mark the locations of more intense gamma-ray sources.
“The bright, steady gamma-ray glow of the Milky Way is punctuated by intense, days-long flares of near-light-speed jets powered by supermassive black holes in the cores of distant galaxies,” said Dr. Seth Digel, a senior staff scientist at SLAC National Accelerator Laboratory.
“These dramatic eruptions, which can appear anywhere in the sky, occurred millions to billions of years ago, and their light is just reaching Fermi as we watch.”
“One of the first things to strike your eye in the movie is a source that steadily arcs across the screen,” said Dr. Judy Racusin, a researcher at NASA’s Goddard Space Flight Center.
“That’s our Sun, whose apparent movement reflects Earth’s yearly orbital motion around it.”
Most of the time, Fermi’s Large Area Telescope (LAT) detects the Sun faintly due to the impact of accelerated particles called cosmic rays. When they strike the Sun’s gas or even the light it emits, gamma rays result.
At times, though, the Sun suddenly brightens with powerful eruptions called solar flares, which can briefly make our star one of the sky’s brightest gamma-ray sources.
“The new movie shows the sky in two different views,” the astronomers said.
“The rectangular view shows the entire sky with the center of our Galaxy in the middle.”
“This highlights the central plane of the Milky Way, which glows in gamma rays produced from cosmic rays striking interstellar gas and starlight.”
“It’s also flecked with many other sources, including neutron stars and supernova…
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