A team of astronomers announces that they have detected 72 incredibly bright and fast flashing events 4 billion light-years away. Their origin remains unknown for the moment.
These mysterious explosions are similar in brightness to supernovae — explosions that signify the end of a star’s life. Supernovae explosions illuminate the sky for several months or more. However, these 72 mysterious explosions were more fleeting, visible from a week to a month maximum — which is incredibly short astronomically. So what are they?
You can see in yellow on the graph below two examples of these newly detected events, and compare them to two typical types of supernovae (red and purple).
These fast and transient events were detected in the data of the Dark Energy Survey Supernova (DES-SN) program, the result of an international collaboration to chase supernovae to better understand dark energy, this hypothetical force that would be the driving force behind the expansion of our Universe. The researchers spotted several supernovae, but they also noticed a number of other faster explosions inside the data – and they are not sure what is causing them.
Below is one of the transient events, which occurred 4 billion years ago, photographed eight days before, and 18 days after:
“The DES-SN study is here to help us understand dark energy, itself totally unexplained,” says one of the astronomers, Miika Pursiainen, from the University of Southampton (UK). “With the detection of these new events, our work confirms that astrophysics and cosmology are still sciences with many unanswered questions! ”
All we know so far is that these events are both incredibly hot and large – with temperatures ranging from 10,000 to 30,000 degrees Celsius. The explosions also vary in size, ranging from several times to one hundred times the distance of Earth to the Sun, which is about 150 million kilometers. Even stranger, the explosions seem to expand and cool as they evolve over time.
How do scientists explain this phenomenon? Some ideas are proposed. One of them suggests that the star was surrounded by a cocoon of dust that it had already ejected – only visible after the dust had been washed away by the supernova’s shock wave. It could also be an entirely new astronomical phenomenon.
To test these hypotheses – or to suggest others – the team will need a lot more data.