Sunday, February 13, 2022

Fermi's 12-year View of the Gamma-ray Sky

 

Credit: NASA/EGRET Team and NASA/DOE/Fermi LAT Collaboration
Hi-Res Zoomable Still Image

This animation cycles between images that encapsulate decades of progress in gamma-ray astrophysics. The lower-resolution image shows the sky as seen by the EGRET instrument aboard NASA's Compton Gamma-Ray Observatory (1991 to 2000) using gamma rays above 100 million electron volts. Lighter colors indicate greater numbers of gamma rays. The most prominent feature is the central plane of our galaxy, which runs across the middle of the map, a result of gamma rays produced when accelerated particles strike interstellar gas and starlight. The largest yellow spot on the right side of the galactic plane is the Vela pulsar, one of five new gamma-ray pulsars EGRET discovered. The prominent reddish blob at top right is the blazar 3C 279. The all-sky map produced by Fermi's Large Area Telescope (LAT), using 12 years of data, is sharper, more detailed, and shows gamma rays of much higher energy than EGRET's. In its first five years, the LAT detected more than 10 times the number of gamma-ray sources seen by EGRET and had captured more high-energy gamma rays from a single source, the Vela pulsar, than the total number EGRET detected from all sources.

These all-sky views show how the sky appears at energies greater than 1 billion electron volts (GeV) according to 12 years of data from NASA's Fermi Gamma-ray Space Telescope. (For comparison, the energy of visible light is between 2 and 3 electron volts.) The image contains 144 months of data from Fermi's Large Area Telescope; for better angular resolution, the map shows only gamma rays detected at the front of the instrument's tracker. Lighter colors indicate brighter gamma-ray sources. The images show the entire sky in galactic coordinates, in which the center is the center of our galaxy. The bright midplane of our galaxy runs across the images.

Source/Credit: NASA / GSFC

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