Massive stars (typically weighing from 8 to 20 solar masses) will become a hundred times fainter in visible light, before going supernova.

The universe is a strange yet stunning place. Although mankind is still in the very early stages of its exploration, we are uncovering its secrets step by step. Understanding stars, solar systems, and galaxies are of great importance. By doing so, we consequently better understand our place in the universe.

Studying stars, their evolution, life, and death is a key element for astronomers. Researchers from Liverpool John Moores University and the University of Montpellier have developed an alert system that signals when a massive star is on its way to becoming a supernova.

Solar dimming

According to this new study, massive stars (typically weighing from 8 to 20 solar masses) will become a hundred times fainter in visible light. This happens in the last few months before they die. At this point, stars are in their last phase of life, known as the ‘red supergiant’ phase. The dimming is caused by an accumulation of debris around the star, which obscures its light. A star’s accretion rate was unknown until now.

Researchers simulated how red supergiants might look when embedded in these ‘cocoons’ before the explosion.  There are images of stars that exploded a year after they were taken in old telescope archives. As can be seen in the images, the stars do not yet appear to have constructed a circumstellar cocoon because they appear normal.

Stellar Cocoons

Thus, the cocoon could be assembled in less than a year, with a very fast turnaround time. Benjamin Davies, lead author of the paper from Liverpool John Moores University, says that dense material almost completely obscures the star, making it appear 100 times fainter. “This means that, the day before the star explodes, you likely wouldn’t be able to see it was there,” he explains.

The only time scientists are able to observe supernovae in detail is after they happen. By utilizing this early-warning system, scientists will be able to watch the precursor stars being destroyed in real-time. To do this, numerous telescopes on Earth and space can be made use of. The research was published in Monthly Notices of the Royal Astronomical Society.