Watch: NASA's Fermi captures cosmic fireworks invisible to the bare eye

The animation shows a subset of more than 1,500 light curves collected by the Large Area Telescope over nearly 15 years in space.
Deena Theresa
Still image of a cosmic gamma-ray fireworks show using just a year of data from the Large Area Telescope.
Still image of a cosmic gamma-ray fireworks show using just a year of data from the Large Area Telescope.

NASA’s Marshall Space Flight Center/Daniel Kocevski 

NASA has released an intriguing animated video of the sky in gamma rays, the "highest-energy form of light". Captured by the Large Area Telescope (LAT) aboard NASA's Fermi Gamma-ray Space Telescope, the animation shows activity during observations from February 2022 to February 2023. 

According to a press release, the "pulsing circles represent just a subset of more than 1,500 light curves – records of how sources change in brightness over time – collected by the LAT over nearly 15 years in space". The LAT detects gamma rays with energies ranging from 20 million to over 300 billion electron volts.

"We were inspired to put this database together by astronomers who study galaxies and wanted to compare visible and gamma-ray light curves over long time scales," Daniel Kocevski, a repository co-author and an astrophysicist at NASA’s Marshall Space Flight Center in Huntsville, Alabama, said in a statement. "We were getting requests to process one object at a time. Now the scientific community has access to all the analyzed data for the whole catalog."

The data is now available in a continually updated interactive library. A paper on the same was published on March 15, 2023, in The Astrophysical Journal Supplement Series.

The animation reveals the central plane of the Milky Way galaxy and the Sun's annual trajectory

"In 2018, astronomers announced a candidate joint detection of gamma rays and a high-energy particle called a neutrino from a blazar for the first time, thanks to Fermi LAT and IceCube," said co-author Michela Negro, an astrophysicist at the University of Maryland, Baltimore County, and NASA’s Goddard Space Flight Center in Greenbelt, Maryland. 

Blazars, which form over 90 percent of the sources in the dataset, are central regions of galaxies that comprise active supermassive black holes. These, in turn, produce particle jets pointed directly at Earth. 

Each frame in the animation shows three days of observations. According to the release, "each object's magenta circle grows as it brightens and shrinks as it dims". The reddish-orange band running across the middle of the sky is the central plane of our Milky Way galaxy, known to be a consistent gamma-ray producer. And the yellow circle reveals the Sun's annual trajectory across the sky.

Collating the catalog took over 400 computer years of processing time and distributed over 1,000 nodes on a computer cluster located at the SLAC National Accelerator Laboratory in Menlo Park, California. That would be three months.

Study Abstract:

The Fermi Large Area Telescope (LAT) lightcurve repository (LCR) is a publicly available, continually updated library of gamma-ray lightcurves of variable Fermi-LAT sources generated over multiple timescales. The Fermi-LAT LCR aims to provide publication-quality lightcurves binned on timescales of 3, 7, and 30 days for 1525 sources deemed variable in the source catalog of the first 10 yr of Fermi-LAT observations. The repository consists of lightcurves generated through complete likelihood analyses that model the sources and the surrounding region, providing fluxes and photon indices for each time bin. The LCR is intended as a resource for the time-domain and multimessenger communities by allowing users to search LAT data quickly to identify correlated variability and flaring emission episodes from gamma-ray sources. We describe the sample selection and analysis employed by the LCR and provide an overview of the associated data access portal.

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