HUNT FOR THE UNIVERSE'S MISSING STARS

An international team of astronomers is on the hunt for objects that should be impossible

- Giles Sparrow

Stars don’t just vanish – or do they? For thousands of years astronomers accepted the idea that the lights in the sky were fixed and unchanging.

Even when it became clear that these lights were actually physical objects like the Sun, one of the key assumptions for astrophysicists has been that they go through major changes very slowly, on timescales of millions or billions of years.

And when the most massive stars of all – which are many times heavier than the Sun – do go through sudden and cataclysmic changes as they reach the ends of their lives, their passing is marked by the unmissable cosmic beacon of a supernova explosion, which shines for many months and may even be visible across hundreds of millions of light years.

But what if some stars suddenly just wink out of visibility? According to everything we know about stars, that should be impossible, but over the past few years a group of astronomers has set out to see whether such impossible things do happen, comparing data across decades of observations.

“VASCO is the Vanishing and Appearing Sources during a Century of Observations project,” explains Dr Beatriz Villarroel of the Nordic Institute for Theoretical Physics, Sweden. “We’re actually interested in all kinds of vanishing objects, but ideally I’d like to find a star that’s been steady and has been there in the sky for as long as we can remember and as long as we have data for, and one day it just vanishes. And you can point the biggest telescopes in the world at it and still see nothing there.”