2023-06-23 08:51:00
An international research group has for the first time observed evidence of a collision between two stars, or remnants of two stars, near a supermassive black hole. The US research institute NOIRLab, whose telescope was used to study the destruction, has so far only been able to assume that stars can also die in this way. It is possible that such events are happening more frequently and are just too well hidden in the chaotic environment of supermassive black holes. The collision described now with the designation GRB 191019A would then be a rare exception. Nevertheless, the research team hopes to be able to observe more such collisions.
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Hope for more long gamma bursts
The gamma-ray flash generated during the collision was discovered on October 19, 2019 with the US space agency NASA’s Swift space telescope. It was noticeable that it lasted more than a minute. Such signals are considered “long” if they are longer than two seconds. The fading afterglow was then studied with the Southern Gemini Observatory in Chile to find out what was responsible. It was not only found that the origin was comparatively close to the center of an old galaxy, but also that it must have been the collision of two compact objects, explains study leader Andrew Levan from Radboud University Nijmegen in the Netherlands.
In normal galactic environments, collisions between the remains of two stars should be extremely rare, the research team writes. But the centers of old galaxies are anything but normal. There, millions of stars could be crowded into an area a few light-years across. Isolated collisions are then possible, especially if the region is still under the gravitational influence of a supermassive black hole. That would force the stars into chaotic orbits where two could collide and cause gigantic explosions. They could be seen at extremely large distances – if the traces are not swallowed up by dust and gas.
That the life of stars can end in such areas has only been assumed so far, the group explains. There are now four possible ways for stars to die. Comparatively small stars like our sun eventually become white dwarf stars, while massive stars explode and end up as neutron stars or black holes. Star remnants can also form binary systems and eventually collide there. All of this is much more predictable than what has now been observed. The find is presented in the journal Nature Astronomy. In order to be able to observe more such events in the future, the research team is hoping above all for the Vera C. Rubin Observatory, which is scheduled to start work in 2025.
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