It’s a cosmic game of hide-and-seek. A team of astronomers say that the next search for advanced extraterrestrial civilisations should look for stars – or even galaxies – that have vanished without a trace, as anything so unexplainable could only be due to life far more intelligent than us.
Beatriz Villarroel at Uppsala University in Sweden says this crazy idea has been gnawing at her since her first year of graduate studies. Now she and two undergraduates have finally taken the plunge. They scoured multiple surveys of the night’s sky by eye in order to see if any of nearly 300,000 light sources disappeared from one survey to the next.
So far the results are mixed. The team found one interesting artefact that looks like it might have vanished, but they can’t be sure. “It was a depressing case in the sense that we neither could reject it and neither could we say that it was a real candidate,” says Villarroel. Although the team checked for so-called false positives, throwing out hundreds of similar disappearing objects, this one withstood all tests – but only just.
Even if the disappearance is real, there could still be an astrophysical explanation. Quasars – the bright centres of galaxies powered by supermassive black holes – can shut down in less than a decade and drop drastically in brightness. Stars, too, can be highly variable.
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