2023-06-26 15:39:09
A group of astronomers claims to have discovered that stars can also die through interstellar collisions, a new form of death that had previously only been theorized, as detailed in a study published on Thursday (22.06.2023) by the journal Nature.
Normally, the final fate of a star depends on its mass: “Large stars end up forming a supernova (a gigantic explosion), and those with a small mass, such as Sun, they dim like a white dwarf,” explained lead author Andrew Levan of Radboud University in the Netherlands.
Death following an interstellar collision
In other less common cases, the stars of neutrons — one of the possible remnants of a supernovathe other is a black hole– they can merge when they’re in a binary system, like a pair of objects born too close to each other.
However, according to the researchers, that is not what happened in October 2019, when there was a burst of colossal energy gamma rays, coming from a distant galaxy located towards the constellation of Aquarius: “Instead of a natural end , stars can die in a collision,” said astrophysicist Levan.
Keys to a galaxy 2 billion light years from Earth
Depending on its duration, which ranges from less than two seconds to several minutes, an event of this type means, respectively, the merger of two neutron stars or the explosion of a large supernova. This burst, named GRB191019, lasted for more than a minute, so it normally belonged to the second category.
But astronomers have seen no signs of supernova in the galaxy in which the jet originated and which is regarding 2 billion light-years from Earth. That’s not surprising at all, because this ancient galaxy hardly generates any more stars anymore, and therefore certainly no longer forms massive stars that are likely to go supernova.
Meeting in the heart of the galaxy
A long observation of the event occurred at an extremely close distance from the galaxy’s nucleus, less than a hundred light-years away. For comparison, the Solar System is regarding 27,000 light-years from the center of the galaxy. This galactic core “is a very dense region, which can contain tens of millions of stars, which can collide or scatter,” added Andrew Levan.
Especially since the “compact objects” that populate it, white dwarfs, neutron stars and small black holes, are subject to the gravitational force of the supermassive black hole, which lurks in the center of the galaxy. This led the international team of researchers to conclude that the two celestial objects whose collision caused the gamma-ray burst “formed in different places from each other and found themselves” in the heart of the galaxy, according to the astrophysicist.
Astronomers believe that such collisions, the existence of which has only been theoretically assumed, can routinely occur in such an environment. In any case, their observation is made very difficult because the hearts of galaxies are regions filled with dust and gas.
JU (afp, rtre)
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