Fermi Gamma-ray Space Telescope

Artist's impression of Fermi
Credit: NASA

The Fermi Gamma-ray Space Telescope (often called Fermi) observes the highest-energy wavelengths of light in the Universe, gamma rays. The Earth's atmosphere blocks gamma rays, so Fermi observes from a low-Earth orbit in space.

The goals of Fermi were to learn more about high-energy objects and events. Objects like quasars and active galactic nuclei powered by black holes. Events like the deaths of massive stars which result in pulsars, neutron stars, and supernovae. It also aimed to learn more about the source of gamma-ray bursts (energetic explosions in distant galaxies). Closer to home, Fermi would also study gamma-rays emitted by our Sun as solar flares.

Fermi was launched on 11 June 2008. It contains 2 scientific tools: the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM). 

The LAT can survey a wide area of the sky to locate high-energy events from several sources. It can see one-fifth of the sky at any one time. 

Animation of a gamma-ray pulsar
Gamma-ray pulses from the Vela Pulsar
Credit: R Romani, Stanford

The GBM the Gamma-ray Burst Monitor must also watch a wide area of the sky. This is because gamma-ray bursts come from random directions. The GBM is made up of 12 detectors which work together to watch the entire sky (apart from the parts blocked by the Earth).

Fermi's biggest discoveries:

  • A pulsar which only emitted gamma-ray light.
  • The most energetic gamma-ray burst ever recorded.
  • High-energy light ever seen from the Sun.
  • Supernovae remnants produce cosmic rays.
  • Active galactic nuclei only produce a small amount of the total gamma-ray background
  • Bubbles of gamma-rays and x-rays around the Milky Way (they have been nicknamed Fermi bubbles).