A team of astronomers announced having detected 72 incredibly bright and rapidly flashing events 4 billion light years away. For the moment, their origins remain unknown.
These mysterious explosions are similar in luminosity to supernovae -explosions that signify the end of a star’s life. But supernovae light up the sky for several months or more. By contrast, these 72 mysterious explosions were more fleeting, visible for only a week to a month maximum -which is incredibly short in astronomical terms. So what are they?
In yellow lines on the chart below, you can see two examples of these newly detected rapid events, and compare them with two types of typical supernovae (indicated in red and purple).
These rapid and transitory events were detected in data collected by the Dark Energy Survey Supernova (DES-SN) programme, the results of an international collaboration aiming to seek out supernova. Their goal is to better understand dark energy, the hypothetical force that could be what is driving the expansion of our universe. The researchers observed several supernovae, but they also noticed within the data a certain number of other faster explosions -and they are not sure what is causing them.
Here is one of the transitory events, coming from 4 billion light years away, photographed from 8 days before maximum brightness to 18 days afterwards:
“The DES-SN survey is there to help us understand dark energy, itself entirely unexplained”, says one of the astronomers, Miika Pursiainen of Southampton University (UK). “Our work confirms that astrophysics and cosmology are still sciences with a lot of unanswered questions!”
All we know until now is that these events are both incredibly hot and very large -with temperatures going from 10,000 to 30,000 degrees Celsius. The explosions vary in size, going from several times to a hundred times the distance between the Earth and the sun, which is around 150 million kilometers. Stranger still, the explosions appear to expand and cool down as they evolve over time.
So how do scientists explain this phenomenon? A few ideas have been put forward. One such idea suggests that in such events, the star is surrounded by a cocoon of dust that it had previously ejected, only becoming visible after the dust is washed away by shock waves from the supernova. It could also be an entirely new astronomical phenomenon.
In order to test out these hypotheses -or to suggest others -the team needed much more data. Suffice to say that it won’t be the last you hear about these 72 explosions. Further results were due to be presented on Tuesday 3 April at the European Week of Astronomy and Space Science in Liverpool.