Because the limb of the Earth is an extremely bright source of high-energy gamma rays from galactic cosmic rays that skim the upper atmosphere, only gamma rays with arrival directions within 100 degrees of the zenith were included. The maps are based on Pass 8 source class gamma rays, and for a reasonably good combination of photon statistics and per-photon angular resolution, photons with energies of 200 MeV or greater were selected. Because the LAT has an extremely broad field of view and its orientation is shifted on alternate orbits, it normally observes the entire sky several times every day. The individual frames of the animation are spatially and temporally smoothed maps of gamma-ray intensity observed by the Fermi LAT between Aug. This is a result of processing data across several days to sharpen the images. Not seen in the time-lapse are many short-duration events that Fermi studies, such as gamma-ray bursts, the most powerful cosmic explosions. Other bright blazars are more than twice as distant, and together provide striking snapshots of black hole activity throughout cosmic time. For example, the light from a blazar known as 4C +21.35 has been traveling for 4.6 billion years, which means that a flare up we see today actually occurred as our Sun and solar system were beginning to form. Many of these galaxies are extremely far away. Somehow, the black holes produce extremely fast-moving jets of matter, and with blazars we’re looking almost directly down one of these jets, a view that enhances their brightness and variability. Each of these galaxies, called blazars, hosts a central black hole with a mass of a million or more Suns. Most of these are actually distant galaxies, and they’re better seen in a different view centered on our galaxy’s north and south poles. Above and below this central band, we’re looking out of our galaxy and into the wider universe, peppered with bright, rapidly changing sources. It’s also flecked with many other sources, including neutron stars and supernova remnants. This highlights the central plane of the Milky Way, which glows in gamma rays produced from cosmic rays striking interstellar gas and starlight. The rectangular view shows the entire sky with the center of our galaxy in the middle. The movie shows the sky in two different views. Brighter colors mark the locations of more intense gamma-ray sources. For comparison, visible light has energies between 2 and 3 electron volts. The movie shows the intensity of gamma rays with energies above 200 million electron volts (MeV) detected by Fermi’s Large Area Telescope (LAT) between August 2008 and August 2022. Gamma rays are the highest-energy form of light. Our Sun, occasionally flaring into prominence, serenely traces a path through the sky against the backdrop of high-energy sources within our galaxy and beyond. The cosmos comes alive in an all-sky time-lapse movie made from 14 years of data acquired by NASA’s Fermi Gamma-ray Space Telescope. Watch this video on the NASA Goddard YouTube channel. Music: "Expanding Shell" written and produced by Lars Leonhard.Ĭredit: NASA's Goddard Space Flight Center Fermi Deputy Project Scientist Judy Racusin narrates this movie, which compresses 14 years of gamma-ray observations into 6 minutes.Ĭredit: NASA’s Goddard Space Flight Center and NASA/DOE/LAT Collaboration
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