Our Sun once had an ‘evil twin’ called Nemesis

Did our sun once have an ‘evil twin’ called Nemesis – which wiped out the dinosaurs by triggering an asteroid strike millions of years ago?

Astronomers have long sought proof of a ‘twin’ star – and now a new study suggests that Nemesis probably did exist (although there’s no evidence it really did kill the dinosaurs).

‘We are saying, yes, there probably was a Nemesis, a long time ago,’ said study co-author Steven Stahler, a UC Berkeley research astronomer.

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Stahler and his team believe that almost all stars form as binary ‘twins’ – but that our sun’s twin has become lost among the stars.

‘We ran a series of statistical models to see if we could account for the relative populations of young single stars and binaries of all separations in the Perseus molecular cloud, and the only model that could reproduce the data was one in which all stars form initially as wide binaries. These systems then either shrink or break apart within a million years.’

A ‘wide binary’ is when the two stars are separated by more than 500 astronomical units – where one AU is the average distance between the sun and Earth (93 million miles).

So Nemesis would have been 17 times farther from the sun than its most distant planet today, Neptune.

Based on this model, the sun’s sibling most likely escaped and mixed with all the other stars in our region of the Milky Way galaxy, never to be seen again

Sarah Sadavoy, a NASA Hubble fellow at the Smithsonian Astrophysical Observatory says, ‘The idea that many stars form with a companion has been suggested before, but the question is: how many?

‘We now believe that most stars, which are quite similar to our own sun, form as binaries. I think we have the strongest evidence to date for such an assertion.’