Trinity astronomers mystified by disappearance of massive star in deep space

30 Jun 2020

An artist’s impression of the missing star before its disappearance. Image: ESO/L Calçada

A team of Trinity College Dublin researchers has reported the disappearance of an unstable, massive star in deep space.

In the vastness of the universe, it can be easy for something to disappear, including a massive star. A team of astronomers led by Prof Jose Groh’s group from Trinity College Dublin (TCD) has reported the disappearance of an unstable massive star in a distant galaxy in the Monthly Notices of the Royal Astronomical Society.

The missing star was noticed using the European Southern Observatory’s Very Large Telescope (VLT), which could indicate that either the star became less bright and partially obscured by dust, or that it collapsed into a black hole without creating a supernova.

Andrew Allan, project leader and a TCD PhD student, said that if the latter is true, it would be the first direct detection of such a monster star ending its life in this manner.

“It would be highly unusual for such a massive star to disappear without producing a bright supernova explosion,” he said.

Massive star ‘going gently into the night’

The mysterious, massive star located in the Kinman dwarf galaxy, approximately 75m light years away, was under observation between 2001 and 2011 and was believed to be in a late stage of its evolution.

However, during follow-up observations using the VLT in 2019, the researchers could no longer find the tell-tale signature of the star. The original survey of the dwarf galaxy showed evidence for a ‘luminous blue variable’ star approximately 2.5m times brighter than the sun.

These unstable stars show occasional dramatic shifts in their spectra and brightness, but they should leave traces astronomers can detect. While a number of other instruments were trained at the star’s location, nothing could be found.

Speaking of this cosmic mystery, Groh said: “We may have detected one of the most massive stars of the local universe going gently into the night.

“We will likely need to wait a few years before confirming what fate befell this particular star. We will observe the galaxy again with the Hubble Space Telescope next year, which will provide new clues.”

Colm Gorey was a senior journalist with Silicon Republic