Science is all about learning new things and challenging our ignorance, but sometimes what we discover tells us just how little we know. New research presented at the European Week of Astronomy and Space Science (EWASS) is one of these cases.
Miika Pursiainen of the University of Southampton and his collaborator observed 72 stellar explosions in the Dark Energy Survey Supernova (DES-SN) Programme. While the explosions have a maximum brightness similar to different regular supernovae that explode when they've run out of fuel and collapse on their core, these ones don’t last as long. They can disappear from within a week to a month, while supernovae can remain bright for several months.
“The fact that we found such a large sample of these unexplained events shows that there is still a lot we do not understand," Pursiainen told IFLScience. "As the events actually appear to be surprisingly common, it is important to understand what they are from an astrophysical point of view. For instance, if we assume they originate in core-collapse supernovae, these events could have an influence on our understanding of stellar evolution."
The team doesn't have enough information to confirm the true nature of these stellar explosions, but they have some ideas based on what they saw. The events are large, from several times to hundreds of times the distance between the Earth and the Sun. They are hot as well, with temperatures ranging between 10,000 and 30,000 degrees Celsius. They also appear to be expanding and cooling, just like a supernova would.
The team suggests the exploding star is shrouded in material that it shed beforehand. When it explodes, this material is heated to high temperatures, so we are seeing the effect on the gas rather than the star itself. Researchers have recently spotted something like this using the Kepler telescope.
“The recent event discovered by Kepler appears to be similar to our sample of events. There is also a number of other studies within the last 5 to 10 years describing similar events. The total number before our study was in order of 30 or so,” Pursiainen continued. “What they are, however, is difficult to answer for now. The events appear to be found in star-forming galaxies, which is why we have been mostly considering scenarios involving core-collapse supernovae.”
The DES-SN’s goal is to explain the nature of dark energy, the alleged cause of the accelerated expansion of the universe. It is designed to spot transient events like supernovae. The team has used data from the first four years of the survey, so the next step will be to look for these explosions in the fifth year. The researchers hope to estimate how common these explosions are and hopefully learn what causes them.
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