WASHINGTON — An international team of astronomers discovered a supernova that might provide an unprecedented look at the first moments of a violent stellar explosion.
The papers published in the latest The Astrophysical Journal described a mysterious signature in the light from the explosion’s first hours.
This category of supernova, called “Type Ia,” generates many of the elements around us but the mechanism that sets off a Type Ia supernova explosion has remained elusive, according to the researchers.
Astronomers have long tried to get detailed data at the initial moments of the explosions and for the first time, they succeeded in February to discover a Type Ia supernova called ASASSN-18bt within the first day after its explosion.
The astronomers realized that ASASSN-18bt looked unusual during its first couple of days.
“Many supernovae show a gradual increase in the light they put out,” said Maria Drout, assistant professor at the University of Toronto and co-author on the discovery paper.
“But for this event, you could clearly see something unusual and exciting happening in the early times, some unexpected additional emission,” said Drout.
Type Ia supernovae are thought to originate from the thermonuclear explosion of a white dwarf star, the dead core left over by a Sun-like star after it exhausts its nuclear fuel. Therefore, material must be added to the white dwarf from a companion star to trigger the explosion, but the nature of the companion star and how the fuel is transferred has long been debated.
Scientists have presumed that additional light seen during the supernova’s early times could be from the exploding white dwarf colliding with the companion star. However, ASASSN-18bt’s early brightness doesn’t quite fit predictions, according to the study.
The new discovery supported a new hypothesis that there might be two distinct populations of Type Ia supernovae, those that show early emission and those that do not, without the need for a nearby star.
“We are finding that supernova explosions are more complicated than we previously thought,” said the study’s lead author Ben Shappee with University of Hawaii.