Astronomers investigating mystery of gargantuan star after it goes out without a bang

Jessica Carpani
what the luminous blue variable star in the Kinman Dwarf galaxy could have looked like before its mysterious disappearance - Shutterstock 

Astronomers have been left puzzled as they investigate the mystery of a gargantuan star that has gone out without a bang.

Located more than 70 million light-years away in the constellation of Aquarius, the star, a part of the Kinman Dwarf galaxy, was first discovered over a decade ago.

Burning 2.5 million times brighter than the Sun, the “luminous blue variable” first caught astronomers' attention when evidence of its existence was noted between 2001 and 2011. 

However, in 2019, they were surprised to find they could no longer see the telltale signatures of the juvenile star, aged somewhere between 2.8 and 3.9 million years old.

The luminous blue variable (LBV), which are usually unstable stars prone to giant outbursts over the course of their life, had disappeared into the darkness of another galaxy - without so much as a bang.

"We were surprised to find out that the star had disappeared," said Andrew Allan, a PhD student at Trinity College Dublin, Ireland, who led the research.

His team, who have been investigating the cosmic mystery, have now offered up two possible explanations for why it might have vanished without a trace.

The first being that the “massive star” may have collapsed into a black hole without exploding as a bright supernova - a luminous stellar explosion that occurs during the last evolutionary stages of a massive star.

Such a hypothesis "would be the first direct detection of such a monster star ending its life in this manner," said Mr Allan.

He added: "It would be highly unusual for such a massive star to disappear without producing a bright supernova explosion."

Jose Groh, also of Trinity College Dublin and one of the study authors, said: "We may have detected one of the most massive stars of the local universe going gently into the night."

 a wide-field view shows the region of the sky, in the constellation of Aquarius, where the Kinman Dwarf galaxy can be found - Shutterstock

They said that if the star collapsed into a black hole without producing a stellar explosion, it would be "a rare event", as "our current understanding of how massive stars die points to most of them ending their lives in a supernova".

Alternatively, it may be partially obscured by a dust cloud and therefore not currently detectable.

At 75 million light-years away, the astronomers have been using the European Southern Observatory's Very Large Telescope (VLT), located in the Chilean Atacama Desert, to observe the star.

They were able to confirm its presence in data collected by the team that showed the LBV’s unique chemical signature.

The researchers, who published their findings in the Monthly Notices of the Royal Astronomical Society, said further studies are needed to understand what happened to the star.