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If we want to spot messages from aliens, looking towards supernovae could help. Intelligent aliens might choose to transmit evidence of their presence during such explosive cosmic events because it would mean they would be more likely to be spotted by anyone looking in that direction, according to researchers from the in California.

Roughly once every 100 years, a star explodes as a supernova in the Milky Way. These flare-ups shine brightly and are visible across the galaxy as the light from the event spreads out. They would even be visible to observers in other galaxies.

The most recent supernova in the Milky Way visible on Earth was SN 1987A, seen for the first time on 23 February 1987, which lasted for several months.

at the Berkeley SETI Research Center in California and her colleagues propose that looking at exoplanets that had also seen the light of supernovae like SN 1987A might be a good idea if we want to find signs of alien life.

鈥淲e can get smart about where we鈥檙e looking,鈥� says Cabrales. 鈥淲e know which [star systems] have seen this big, bright event. So which one of those has had enough time to see this event and send a signal to us?鈥�

In work presented at the in Seattle in early January, Cabrales identified 32 stars using NASA鈥檚 Transiting Exoplanet Survey Satellite whose planets could be good targets for further study, having been close enough that anything living on planets there may have been able to see the supernova and had time to transmit their presence.

There will be other star systems in future too that gradually also see the light of the supernova, which would make good future targets, she said.

What our attempts to communicate with alien civilisations say about us

From serious efforts to declare our presence to extraterrestrial civilisations to daft publicity stunts, we have been sending messages to space for decades. What should a new postcard to the stars say?

at Pennsylvania State University says the idea could be a good way to rank stars that we should target to hunt for intelligent life. 鈥淭here鈥檚 an enormous amount of stuff to look through,鈥� he says. 鈥淭his adds to the list of ways in which we can prioritise stars.鈥�

It might also make sense for us to transmit our presence more broadly the next time we see a supernova, if we want anything that is employing the same search method on another planet to spot us. 鈥淚f a supernova were to go off right now, I say we send a signal,鈥� says Cabrales. 鈥淢aybe someone will see it.鈥�

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