Astronomy sometimes reserves unexpected observations for us, as illustrated by the stellar explosion SN 2022esa. It displayed a regular and stable behavior for several weeks, contrary to what one might expect from a supernova.
An international team studied this phenomenon by combining the capabilities of two powerful instruments. The Subaru telescopes in Hawaii and Seimei in Japan thus enabled the collection of precise data. The explosion having occurred in a distant galaxy, located some 320 million light-years away, astronomers were able to follow its evolution with great precision, which brought to light unexpected characteristics.
The analyses point towards a specific type of star, known as a Wolf-Rayet star. These stars are very hot, luminous, and at the end of their lives, having lost a large part of their gaseous envelope. Their explosion is usually violent with the core collapsing into a black hole, but the stability observed here indicates the presence of a companion that likely played a regulating role. This massive star was therefore not evolving alone in its stellar environment.
Everything suggests that the star was orbiting another object, probably another black hole or a massive star destined to become one. During the supernova, the Wolf-Rayet star disappeared, leaving behind this partner. Eventually, and if it is a star, this partner could also transform into a black hole, thus forming a pair of black holes orbiting each other.
This discovery highlights the advantage of combining different observation tools. The Seimei telescope offers fast reactivity to capture transient events, while Subaru provides high sensitivity allowing for a detailed study. Their collaboration enables the capture of brief phenomena and the extraction of information on the dynamics of stellar explosions.
The researchers anticipate that this approach will lead to further progress. The study of astronomical transient phenomena, like supernovae, could reveal more elements about the formation of compact objects. Keiichi Maeda of Kyoto University notes in a statement that this offers a new avenue for tracing the evolutionary history of massive stars.
This work adds a significant piece to the puzzle of stellar astrophysics. It demonstrates how the death of a star can mark the beginning of the birth of exotic binary systems.