As many as 72 extremely fast and bright celestial events that for now cannot be explained, have been observed by a team of astronomers.
They are transient phenomena but still very strange, says researcher Miika Pursiainen of the University of Southampton, who along with his collaborators found the largest number of these quick events to date.
Pursiainen presents the results of of the observations on 3 April, 2018 at the European Week of Astronomy and Space Science.
Images of one of the transient events, from eight days before the maximum brightness to 18 days afterwards. This outburst took place at a distance of 4 billion light years. Credit: M. Pursiainen / University of Southampton
The events appear to be both hot, with temperatures from 10,000 to 30,000 degrees Celsius, and large ranging in size from several up to a hundred times the distance from Earth to Sun (the Earth is 150 million kilometres from the Sun). They also seem to be expanding and cooling as they evolve in time, as would be expected from an exploding event such as a supernova.
While they have a similar maximum brightness to different types of supernovae they are visible for less time, from a week to a month. In contrast supernovae last for several months or more.
DES-SN survey that uses a large camera on a 4-metre telescope in the Cerro Tololo Inter-American Observatory (CTIO) in the Chilean Andes, has contributed to this discovery.
The survey looks for supernovae, the explosion of massive stars at the end of their lives. A supernova explosion can briefly be as bright as a whole galaxy, made up of hundreds of billions of stars.
There is no clear explanation on the origin of these transients. One possible scenario is that the star sheds a lot of material before a supernova explosion, and in extreme cases could be completely enveloped by a shroud of matter. The supernova itself may then heat the surrounding material to very high temperatures. In this case astronomers see the hot cloud rather than the exploding star itself. To confirm any of this, the team will need a lot more data.
“The DES-SN survey is there to help us understand dark energy, itself entirely unexplained. That survey then also reveals many more unexplained transients than seen before,” Pursiainen says.
“If nothing else, our work confirms that astrophysics and cosmology are still sciences with a lot of unanswered questions!”
The team plan to continue their search for transients, and estimate how often they take place compared with more ‘routine’ supernovae.
Research will be presented on Tuesday 3 April, 2018 at the European Week of Astronomy and Space Science.