Somewhere in a faraway galaxy, a star has vanished, leaving experts stumped. A massive star in a distant galaxy has disappeared, and our telescopes can’t pinpoint it anymore. Using the Very Large Telescope (VLT) from the European Southern Observatory (ESO), a team of astronomers has discovered the absence of a massive unstable star in a distant dwarf galaxy.
The star, with a brightness of 2.5 million times more intense than that of the Sun, disappeared without producing a massive supernova explosion. Something that until now has astronomers puzzled, who in the face of what has been observed, have considered a new form of stellar death.
Scientists believe that this could indicate that the star became less bright and was partially obscured by dust.
The new cosmic occurrence has left experts stumped who have already come up with more than one theory trying to explain the mysterious disappearance of the star,
An alternative explanation is that the star collapsed into a black hole without producing a supernova.
“If true, it would be the first direct detection of such a monstrous star that ends its life this way,” says lead author of the discovery and Ph.D. student Andrew Allan of Trinity College, Dublin, Ireland.
Between 2001 and 2011, several teams of astronomers studied this massive star, located in the Kinman dwarf galaxy, and their observations indicated that it was at a late stage in its evolution.
Allan and his collaborators in Ireland, Chile, and the United States wanted to know more about how very massive stars end their lives, and the object of this dwarf galaxy seemed like the perfect target.
But when they pointed ESO’s VLT at the distant galaxy in 2019, they could no longer find the star’s telltale footprints; in other words, it had disappeared.
Instead of finding the star, the astronomers found it had disappeared.
Located about 75 million light-years away, in the constellation Aquarius, the dwarf Kinman galaxy is too far away for astronomers to see its individual stars, but they can detect traces of some of them.
From 2001 to 2011, light from the galaxy showed consistent evidence that it hosted a “blue light variable” star some 2.5 million times brighter than the Sun.
Stars of this type are unstable and show occasional radical changes in their spectra and brightness.
Even with those changes, the luminous blue variables leave specific traces that scientists can identify, but these were no longer present in the data the team collected in 2019, leaving the question of what had happened to the star in the air.
The strange part is, according to astronomers, that its very unusual for such a massive star to disappeared without producing a bright supernova explosion.
The group of astronomers first pointed the ESPRESSO instrument toward the star in August 2019, simultaneously using the VLT’s four 8-meter telescopes.
But they were unable to find the signs that previously pointed to the presence of the luminous star.
A few months later, the group tested the X-shooter instrument, also on ESO’s VLT, and again found no trace of the star.
According to team member José Groh, also from Trinity College Dublin, “we may have detected the death of one of the most massive stars in the local universe. Our discovery would not have been possible without the use of ESO’s powerful 8-meter telescopes, their unique instrumentation, and rapid access to those facilities following Ireland’s recent agreement to join ESO.”
Previously gathered data suggests that the star may have been experiencing a strong burst period that probably ended sometime after 2011. Blue luminous variable stars of this type are prone to experiencing gigantic bursts throughout their life, causing the rate of mass loss of stars to increase and increasing their luminosity dramatically.
Based on their observations and models, astronomers have suggested two explanations for the star’s disappearance and the lack of a supernova, related to this possible outburst.
One possibility is that the outburst could have resulted in the blue luminous variable transforming into a less luminous star, which could also be partially obscured by dust.
The other possibility is that the star may have collapsed into a black hole without producing a supernova explosion. This would be an unusual event, as our current understanding of how massive stars die suggests that most end their lives by exploding as supernovae.