Most powerful gamma ray burst ever seen came from colliding galaxies
Gamma-ray bursts (GRBs) are already the most energetic events we know of in the universe, and now, astronomers have detected the most powerful gamma ray burst ever. The competition isn’t even close, either – this event is almost a thousand times more powerful than your average GRB.
Such an intensely powerful signal can only come from some of the most energetic events in the cosmos. GRBs are produced when stars go supernova and collapse into either neutron stars or black holes, ejecting massive amounts of plasma at close to the speed of light and throwing out more energy in seconds than the Sun will in its lifetime.
The energy of these bursts is measured in electron volts (eV), where one electron volt is the amount of energy gained by a single electron when accelerated by one volt. For most GRBs, the afterglow is measured in a few dozen giga-electronvolts (GeV), which are billions of electron volts. But this latest detection far outshines that – it registered up to 1 tera-electronvolt (TeV), or a trillion electron volts.
“High-energy GRBs with energies in the region of tera-electron-volts were theoretically predicted,” says Masahiro Teshima, an author of the study. “Astronomers have searched for such powerful bursts for 15 years. My international team and I are proud to announce the discovery of the first gamma-ray burst with observed energies up to 1 tera-electronvolt, by far the highest-energy photons ever detected from a GRB.”
The event in question is named GRB190114C, and it was observed on January 14 this year. It was first spotted by two satellites designed to detect gamma-ray bursts – the Swift Observatory and the Fermi Gamma-ray Space Telescope – and to them, it looked like any other GRB. That’s because the short-lived initial burst is usually weaker, on the order of a few mega-electronvolts (MeV).
But it’s the afterglow, which shines brighter, that’s of particular interest. To watch for that, whenever these instruments detect GRBs they immediately signal to other facilities which can follow up observations. More than 20 other telescopes and observatories around the world focused their attention onto the spot to watch the celestial fireworks.
The afterglow began about a minute after the initial burst, and lasted about 20 minutes total. For the first 30 seconds or so, the glow was over 100 times stronger than the Crab Nebula, which is the brightest known gamma ray source in the galaxy. Its energy peaked at 1 TeV, but it lingered for a while down to 0.3 TeV, which is still very strong.
One of the observatories that peered at GRB190114C was Hubble. Although it can’t detect gamma rays, the space telescope was able to help determine how far away the event was, and what kind of conditions may have contributed to its extreme energy. It turns out that the burst came from a galaxy that’s currently colliding with another.
“Hubble’s observations suggest that this particular burst was sitting in a very dense environment, right in the middle of a bright galaxy 5 billion light years away,” says Andrew Levan, a lead author of the study. “This is really unusual, and suggests that this concentrated location might be why it produced this exceptionally powerful light.”
The research was published in the journal Nature.