The Fermi Gamma-ray Space Telescope has been in space for just over 11 years, looking into the cosmos to catch the most powerful explosions in the universe, the so-called gamma-ray bursts (GRBs). These spectacular releases of energy come in different forms; long from supernovae and hypernovae, and short from neutron star collisions. However, the way they are produced remains poorly understood.
The team has now prepared a catalog, published in the Astrophysical Journal, of the 186 GRBs observed in Fermi’s first decade of service by its Large Area Telescope (LAT). And it really shows just how incredibly powerful some of these events can be. Meanwhile, it also shows some of the properties that all these events share.
“Each burst is in some way unique,” co-author Magnus Axelsson, an astrophysicist at Stockholm University, said in a statement. “It’s only when we can study large samples, as in this catalog, that we begin to understand the common features of GRBs. These, in turn, give us clues to the physical mechanisms at work.”
The single most energetic photon detected was in the event GRB 130427A and possessed an energy roughly 35 billion times higher than photons from visible light. The observation of such a powerful event actually challenged a popular model that linked GRBs to the shock wave that jets of high-speed electrically charged particles might experience as they slam into slower material. The model can’t explain this particular event.
Another one for the history books is GRB 080916C, the furthest GRB ever observed, coming to us from 12.2 billion light-years away. Distances are only known for 34 out of the 186 GRBs and researchers were also able to estimate how powerful the event that produced it must have been. Estimated to be an explosion equivalent to 9,000 supernovae, it is the most powerful GRB event ever registered.
NASA also wants to highlight GRB 081102B, the shortest one, lasting just one-tenth of a second, and GRB 160623A, the longest burst in the catalog, which shined brightly for almost 10 hours. There is also GRB 090510, which was used to test Einstein’s idea that light, no matter its energy, moves at the same speed through the vacuum of space.
An important event that wasn’t spotted by the LAT (it was switched off at the time) is the collision between two neutron stars that was first detected by the gravitational wave observatories LIGO and Virgo. It was detected by the Gamma-ray Burst Monitor instrument, which constantly looks at the entire sky and has detected more than 2,300 GRBs to date.