The radiation originates in binary stars that have merged after being ejected from their galaxy. Usually Eruptions that do not occur within a galaxy Lasts a few seconds. In such eruptions, heavy elements including gold and platinum are formed
Gamma-ray bursts are the most powerful explosions in the universe and are usually caused by collapsing stars or collisions of compressed stellar remnants. But a new discovery challenges that understanding, because it doesn’t fit into any of those categories. Astronomers from the Niels Bohr Institute played an important role in this research, which could potentially change current theories about these powerful events.
Daniele Bjorn Malsani made a routine follow-up observation of a gamma-ray burst, named GRB 211211A, using the Nordic Optical Telescope on the Canary Island of La Palma. Normal procedure after receiving the message automatically generated by the Gamma-ray Burst Mission Swift satellite that monitors gamma-ray bursts.
But something didn’t work out…
Malsani is an astronomer at Radboud University in the Netherlands and a visiting researcher at the Cosmic Dawn Center in Copenhagen. He specializes in gamma-ray bursts, the most energetic explosions in the universe.
But to understand what went wrong, let’s first explain what gamma bursts are:
Gamma bursts are short and very bright flashes of the most energetic form of light, gamma rays. They are most often discovered in the very distant universe and usually have two categories which are thought to arise from two different physical scenarios:
“Long” bursts usually last a few seconds to a few minutes but are often accompanied by a longer secondary flash of less energetic light. They are found in star-forming regions compressed by fire in galaxies and are thought to be the result of a massive star collapsing into a compressed neutron star or black hole, ejecting its outer parts in the process in a huge supernova-like explosion.
“Short” bursts pass even faster, their average duration a tenth of a second to a second. They often appear offset from the center of the galaxy or even outside the galaxy. The common theory is that they are the result of two massive stars orbiting each other in a “binary” system. At some point they explode as supernovae, kicking them out of their host galaxy. Eventually, however, the two objects will spiral inward and merge, causing a gamma-ray burst.
In both cases, the energy released is incredible: at peak, they can shine as brightly as all the stars in the observable universe combined (assuming they emit light in all directions equally. In reality, they are probably a little less bright but emit most of their light in narrow jets, when we just happen to be in that direction ).
So what was the problem with the Malsani burst, GRB 211211A? Well, she doesn’t seem to fit either of those categories, or maybe both. “The observations show that the source of the outburst was outside the galaxy that is typical of hosting short outbursts. But it didn’t last a millisecond or a few seconds – this monster lasted almost a minute,” says Malsani.
This strange event prompted an international group of astronomers, led by Gillian Restinged from Northwestern University in the US, to begin an intensive campaign to study this surprising object. This activity led to the completely unexpected discovery of the so-called kilonova, the smoking gun evidence of a collision between two neutron stars, or between a neutron star and a black hole.
It is widely agreed that binary neutron star mergers are the originators of short gamma-ray bursts. Astronomers wondered why this merger was followed by a long outburst.
Luca Izzo, an astronomer at the Niels Bohr Institute, participated in the study. He says: “Gamma bursts can show a variety of behaviors, but the difference between short and long events was clearly established already in the nineties and is considered one of the pillars of the field. This finding really surprised us.”
More on the subject on the science website:
- The race to discover superheavy elements continues
- A burst of gamma rays that lasted almost two hours
- A new type of gamma ray burst shows a new way for a star to die
- The most powerful gamma ray burst ever observed has been recorded
- A new type of gamma ray burst may be discovered