Massive Star Fails to Explode, Forms Black Hole in Rare Discovery

Astronomers have observed a rare cosmic event: the collapse of a massive star directly into a black hole without the dramatic explosion typically associated with stellar death – a supernova. The star, designated M31-2014-DS1, resides in the Andromeda galaxy, approximately 2.5 million light-years from Earth.

Massive stars are expected to end their lives in spectacular supernova explosions. As a star exhausts its nuclear fuel, its core collapses under gravity. This collapse usually triggers a powerful shockwave that tears the star apart, scattering its material into space and leaving behind either a neutron star or a black hole. However, this process doesn’t always unfold as predicted.

In the case of M31-2014-DS1, observations revealed a different fate. Instead of a brilliant supernova, the star gradually dimmed and ultimately disappeared. Archival data indicates that the star was exceptionally bright in infrared light in 2014. By 2023, its luminosity had faded more than 10,000-fold. Researchers believe this fading was caused by the shedding of the star’s outer layers.

The core of the star had exhausted its fuel, losing the outward pressure needed to counteract the immense force of gravity. Normally, this would initiate a powerful shockwave. However, in this instance, the shockwave stalled. Instead of a cataclysmic explosion, most of the star’s material collapsed inward onto the forming black hole. This resulted in the creation of a black hole without the characteristic supernova event.

“This has probably been the most surprising discovery of my life,” says astronomer Kishalay De of Columbia University, who led the research. “The evidence of the disappearance of the star was lying in public archival data, and nobody noticed for years until we picked it out.”

This phenomenon, known as a “failed supernova,” is relatively rare because it’s difficult to detect. Unlike supernovae, which briefly outshine entire galaxies, identifying stars that quietly vanish is a significant challenge. “Unlike finding supernovae, which is easy because the supernova outshines its entire galaxy for a few weeks, finding individual stars that disappear without producing an explosion is remarkably difficult,” De explains.

The study, published in the journal Science, was supported by data collected over several years from NASA’s NEOWISE mission. The fading was observed in infrared light, which is particularly useful for detecting the heat signatures of dust and gas surrounding dying stars. The increase in infrared light prior to the disappearance is thought to be due to the release of these outer layers as the star began to collapse.

The observation provides a new understanding of how black holes can form. While the traditional supernova pathway is well-established, this discovery demonstrates that black holes can also arise through a much quieter process. This finding is crucial for understanding the diversity of black hole formation mechanisms and refining our models of stellar evolution.

“The dramatic and sustained fading of this star is very unusual, and suggests a supernova failed to occur, leading to the collapse of the star’s core directly into a black hole,” De said.

Astronomers are now actively searching for other stars that may be undergoing a similar fate. By studying these “failed supernovae,” scientists hope to gain further insights into the conditions that lead to their formation and the prevalence of this alternative pathway to black hole creation. This research will help to paint a more complete picture of the life cycle of massive stars and the evolution of black holes in the universe.

The discovery highlights the importance of archival data in astronomical research. The initial observations that led to this finding were made years ago, but their significance was not recognized until recently. This underscores the value of preserving and re-analyzing existing data, as it can often reveal unexpected and groundbreaking discoveries.