An Extremely Bright Star Has 'Disappeared' And Scientists Aren't Sure Why

The star had been observed by astronomers for a decade between 2001 and 2011. It was a luminous blue variable star believed to be in the later stages of its life. Stars this far away cannot be observed individually, but scientists were able to detect its signatures.

In 2019, researchers led by Andrew Allan, from Trinity College Dublin, were looking to find out how very massive stars die. Using the European Southern Observatory's Very Large Telescope, they turned their focus to the star in the Kinman galaxy. However, they soon realized it was missing. Initially, conditions for observations were not perfect, so the team tried looking for a second time, allowing them to confirm the star had disappeared. Their findings have been published in the Monthly Notices of the Royal Astronomical Society.

Massive stars that are coming to the end of their lives are unstable and sometimes have huge shifts in their brightness. However, even these changes leave signatures that could be detected by researchers.

What caused the star's disappearance is unclear. The researchers say there are two potential explanations. One is that the star had a massive outburst where it lost a huge amount of brightness and turned into a less luminous star. The star could then have been shrouded in dust, making it look like it had vanished.

The other explanation is that the star collapsed into a black hole without producing a supernova. If this is correct, it would be the first time such a phenomenon had been identified in such a large star.

Allen told Newsweek that at the moment, both explanations are equally viable. "Fortunately, we may be able to rule one out when our team gets to reobserve the galaxy using the Hubble Space Telescope," he said in an email. "Comparing before and after [Hubble] images of the galaxy could verify the star's disappearance. Furthermore, observations at infrared wavelengths could rule out dust, which would be heated by the light of the star causing the dust to give off infrared radiation."

Study co-author Jose Groh, also from Trinity, said computer simulations have previously predicted that some stars will not produce a supernova when they die. "This happens when a massive black hole is formed, and it is not spinning very fast," he told Newsweek in an email. "Such an event has been observed only once, in the galaxy of NGC 6946 where a smaller massive star seemed to disappear without a bright supernova explosion.

"In our case, the star is much more massive and is located in a small galaxy, which makes the finding unique and could hold important clues as to how stars could collapse to a black hole without producing a bright supernova."

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An star 2.5 million times brighter than the sun just disappeared from a galaxy 75 million light-years away. ESO/L. Calçada
An Extremely Bright Star Has 'Disappeared' And Scientists Aren't Sure Why | Tech & Science