Frenzied Activity in the Gamma-ray Sky Captured by NASA’s Telescope

The new animation shows the gamma-ray sky’s frenzied activity during a year of observations by the Large Area Telescope (LAT) aboard NASA’s Fermi Gamma-ray Space Telescope.

The pulsing circles represent just a subset of 1,525 light curves. All these data are now publicly available in a continually updated interactive library.

“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,” said Dr. Daniel Kocevski, an astrophysicist at NASA’s Marshall Space Flight Center.

“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.”

Over 90% of the sources in the dataset are blazars, central regions of galaxies hosting active supermassive black holes that produce powerful particle jets pointed almost directly at Earth.

Ground-based observatories, like NSF’s IceCube Neutrino Observatory in Antarctica, can sometimes detect high-energy particles produced in these jets.

Blazars are important sources for multimessenger astronomy, where scientists use combinations of light, particles, and space-time ripples to study the cosmos.

“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 Dr. Michela Negro, an astrophysicist at the University of Maryland and NASA’s Goddard Space Flight Center.

“Having the historical light curve database could lead to new multimessenger insights into past events.”

In the animation, each frame represents three days of observations.

Each object’s magenta circle grows as it brightens and shrinks as it dims. Some objects fluctuate throughout the entire year.

The reddish orange band running across the middle of the sky is the central plane of our Milky Way Galaxy, a consistent gamma-ray producer.

Lighter colors there indicate a brighter glow. The yellow circle shows the Sun’s apparent annual trajectory across the sky.

Processing the full catalog required about three months, or more than 400 computer years of processing time distributed over 1,000 nodes on a computer cluster located at the SLAC National Accelerator Laboratory in Menlo Park, California.


S. Abdollahi et al. 2023. The Fermi-LAT Lightcurve Repository. ApJS 265, 31; doi: 10.3847/1538-4365/acbb6a