Fermi Gamma-ray Space Telescope

active Mission

NASA's Fermi Gamma-ray Space Telescope is a powerful space observatory that detects gamma rays, the most energetic form of light. Fermi enables scientists to address questions across a broad range of topics, from crushed stellar remnants like pulsars and the origin of high-energy charged particles called cosmic rays to stellar explosions known as gamma-ray bursts.

Mission Type

Space telescope


June 11, 2008


Gamma rays


Extended mission


Fermi observes light with energies thousands to hundreds of billions of times greater than what our eyes can detect. The energy of the light we can see ranges from about 2 to 3 electron volts. Fermi observes light in the energy range between 8,000 electron volts (8 keV) to greater than 300 billion electron volts (300 GeV). As a result, the gamma-ray sky looks spectacularly different than the one we see at night, as shown in the image at the top of the page constructed from 12 years of Fermi observations greater than 1 GeV.

NASA’s Fermi Gamma-ray Space Telescope, illustrated here, scans the entire sky every three hours as it orbits Earth.
Credit: NASA's Goddard Space Flight Center/Chris Smith (USRA/GESTAR)

The satellite launched on June 11, 2008, as the Gamma-ray Large Area Space Telescope. Shortly thereafter, NASA renamed the observatory in honor of Professor Enrico Fermi (1901-1954), a pioneer in high-energy physics.

Since then, Fermi has discovered more than some 300 gamma-ray pulsars, including the first one found beyond our own galaxy. Fermi has shown that giant flares from supermagnetized neutron stars can be detected in galaxies beyond our own. Its measurements have provided important limits on new theories of gravity and of the nature of dark matter, the mysterious substance that seems to bind galaxies together. Fermi data revealed a vast new component of our galaxy known as the Fermi Bubbles, a structure that spans 50,000 light-years and likely formed as a result of an outburst from the monster black hole at the center of our galaxy.

The Fermi Bubbles extend above and below the galactic plane and span about 50,000 light-years. The plane of our galaxy (blue) glows brightly in gamma rays emitted when high-energy particles interact with gas and starlight. The Fermi Bubbles stand out in higher-energy gamma rays (magenta).
Credit: NASA/DOE/Fermi LAT Collaboration

Fermi observed the first light ever seen from an event with detected gravitational waves – the merger of two neutron stars. And for the first time, Fermi data enabled scientists to backtrack a high-energy neutrino to its source – a black-hole-powered galaxy located billions of light-years away.

The spacecraft and the instruments aboard Fermi remain in good health and continue to monitor the sky.

Fermi is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the U.S.

Featured Story

NASA’s Fermi Captures Dynamic Gamma-Ray Sky in New Animation

Cosmic fireworks, invisible to our eyes, fill the night sky. We can get a glimpse of this elusive light show…

Read the Story
Astronomers combined data from NASA's Fermi Gamma-ray Space Telescope, other space missions, and ground-based observatories to reveal the origin of GRB 200826A, a brief but powerful burst of radiation. It’s the shortest burst known to be powered by a collapsing star – and almost didn’t happen at all. Credit: NASA's Goddard Space Flight Center
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