NASA's Fermi Gamma-ray Space Telescope team has produced a 14-year time-lapse movie showcasing the dynamic gamma-ray sky. The footage, created from the data collected by Fermi's Large Area Telescope (LAT) between August 2008 and August 2022, captures the celestial dance of high-energy sources within our galaxy and beyond.
Seth Digel, a senior staff scientist at SLAC National Accelerator Laboratory, crafted the images, revealing the radiant gamma-ray glow of the Milky Way. The time-lapse vividly portrays the sun's graceful journey across the sky, intermittently flaring into prominence.
"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 Digel.
"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," he added.
Time-Lapse in Two Distinct Views
Gamma rays, the highest-energy form of light, are depicted in the movie with energies exceeding 200 million electron volts, as captured by Fermi's LAT. The visualization assigns brighter colors to mark the locations of more intense gamma-ray sources, offering a dynamic perspective on the universe's high-energy events.
Judy Racusin, Fermi Deputy Project Scientist, provides narration for a tour of the movie, emphasizing the sun's apparent movement reflecting Earth's yearly orbital motion.
While the LAT typically detects the Sun faintly due to cosmic rays - accelerated particles traveling at nearly the speed of light - solar flares can briefly elevate our star to one of the sky's brightest gamma-ray sources, according to NASA.
The time-lapse unfolds in two distinct views. The rectangular view encompasses the entire sky, with the center of our galaxy positioned in the middle.
It features the central plane of the Milky Way, aglow with gamma rays generated by cosmic rays colliding with interstellar gas and starlight. The central band also features various sources, such as neutron stars and supernova remnants.
In a different view centered on our galaxy's north and south poles, the movie offers a closer look at distant galaxies, particularly blazars. Each blazar hosts a central black hole with a mass exceeding a million Suns, producing fast-moving jets of matter.
Unique Vantage Point
The unique vantage point, looking almost directly down one of these jets, enhances the brightness and variability of blazars.
Racusin noted that the variations in brightness provide valuable insights into changes occurring in these jets, prompting astronomers to monitor and alert other telescopes when intriguing events unfold.
Although the time-lapse primarily highlights longer-duration events, it does not encompass short-duration phenomena like gamma-ray bursts, which are the most potent cosmic explosions.
This exclusion results from processing data over several days to improve image clarity, showcasing Fermi's crucial role in advancing our continually evolving comprehension of the cosmos.
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