The mystery of the missing star in the Andromeda Galaxy – What really happened?

The case of a missing star from the Andromeda Galaxy has emerged as one of the most intriguing astronomical mysteries of recent years. The yellow supergiant known as M31-2014-DS1 gradually brightened in 2014, only to disappear without a trace from the night sky over the following years. While two research teams are currently investigating the phenomenon, the precise events remain unresolved.

Stars are generally extremely stable objects, with lifespans of billions of years, meaning they rarely undergo dramatic changes in a short period. It is not unheard of for a star to dim or end its life in a colossal supernova explosion before collapsing into a black hole or neutron star. However, it is exceptionally unusual for a star to simply vanish without a trace. This is precisely what makes the disappearance of a star from the Andromeda Galaxy so remarkable.

As reported by IFLScience, M31-2014-DS1 was a yellow supergiant with a mass roughly 12–13 times that of the Sun. Scientists observed it gradually brightening in 2014, yet by 2018 it had completely vanished from view. The case is made more complex by the fact that no conspicuous supernova explosion was observed, raising questions that both research teams are striving to answer.

The missing star and the “failed supernova” hypothesis

One team, analysing data from the James Webb Space Telescope (JWST) and the Chandra X-ray Observatory, concluded that the missing star may represent a striking example of a so-called “failed supernova”. This suggests that the star collapsed directly into a black hole without undergoing the dramatic explosion typically associated with supernovae. According to theory, stars above a certain mass can indeed end their lives in this quiet manner.

During observations, the researchers detected an extraordinary source of light where the star had previously been, but it only emits around 7–8% of the original luminosity. They also observed a shell of dust extending between 40 and 200 astronomical units, which is thought to be the remnants of previously ejected material.

The team proposes that the faint light may originate from the fallback of ejected material and accretion onto the newly formed black hole. The model is not perfect, however, as no X-ray emission indicative of accretion has been detected. The researchers suggest this could be due to the dense dust currently absorbing X-rays, an effect that may diminish as the structure expands.

Questions and alternative explanations

Another research team urges caution. They note several observational details that challenge the idea that the missing star became a “failed supernova”. Their models suggest that if a black hole had formed, the light from fallback material should gradually fade. Observations, however, show that the source has not dimmed significantly.

Further complicating matters, archival Chandra observations from 2015, Swift data from 2020, and more recent Chandra measurements from 2024 have all failed to detect X-ray emission from the location. This conflicts with theories predicting that a newly formed black hole could emit strong X-rays for thousands of years.

According to this second team, the star may indeed be obscured by a thick layer of dust, but another possibility is that the missing object is the result of a stellar merger. Such an event could generate vast quantities of dust, obscuring the central source and leaving behind only a faint, reddish glow.

The mystery remains unsolved

At present, there is no definitive answer as to what happened to the missing star. It may have collapsed into a black hole, in which case the source will continue to fade. Alternatively, a stellar merger may have occurred, and the object could brighten again once the dust disperses.

Researchers emphasise that further observations over the coming years will be essential to solve the mystery, with the James Webb Space Telescope likely to play a central role.

In the meantime, the missing star remains one of the most captivating open questions in astronomy, highlighting that the universe still holds many surprises. Such mysterious processes include, for example, the birth of galaxies, which we explored in a previous article.