This image of the dwarf galaxy PHL 293B was taken with the Wide Field Camera 3 (WFC3) onboard the NASA/ESA Hubble Space Telescope in 2011, before the disappearance of the massive star.
"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.
A huge star observed by astronomers appears to have vanished right before their eyes.
Andrew Allan of Trinity College Dublin, along with colleagues from Chile and the United States, pointed ESO's Very Large Telescope (VLT) in Chile's Atacama Desert towards the distant galaxy in 2019 for a new survey.
Located 75 million light-years away in the constellation of Aquarius, the Kinman Dwarf galaxy is too far away for astronomers to see its individual stars, but they can detect the signatures of some of them.
Between 2001 and 2011, they found evidence of a "luminous blue variable star" about 2.5 million times brighter than our Sun.
"The outburst may have resulted in the luminous blue variable being transformed into a less luminous star, which could also be partly hidden by dust", they said.
When researchers in 2019 made a decision to check in on the tiny galaxy they realized something was missing.
Now, in a new paper published today (June 30) in the journal Monthly Notices of the Royal Astronomical Society, a team of space detectives (see: astrophysicists) attempt to solve the case of the disappearing star by providing several possible explanations.
"We may have detected one of the most massive stars of the local Universe going gently into the night", said Dr. Jose Groh, also of Trinity College Dublin. Stars like this are rare, with only a handful confirmed in the universe so far.
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. An alternative explanation is that the star collapsed into a black hole without producing a supernova.
However, the researchers can't rule out the possibility that the star went supernova in the period between 1995 and 1998 when no observations were available. Image credit: NASA / ESA / Hubble / J. Andrews, University of Arizona. The extremely massive star was of particular interest because scientists still don't know much about how such objects behave towards the end of their lifetimes, especially in metal-poor environments such as the Kinman Dwarf galaxy.
This would be a rare event: our current understanding of how massive stars die suggests a lot of them meet their end in a violent nova. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries.
The archival search also revealed new information. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. ESO's Extremely Large Telescope will have a single 127-foot (39 meters) mirror, compared with the VLT's combined aperture of 107-foot (32 m) mirror across four telescopes.