Every star is born with a companion: Sun had a twin which got the dinosaurs killed by kicking an asteroid to Earth

We all know that our Sun was born 4.5 billion years ago, but what we did not know till now is that it likely had a twin when it came into existence, scientists have said. They have also said that every star in the universe is born with a companion, including the one nearest to Earth called Alpha Centauri, a triplet system.

An explanation in this topic was long sought by astronomers, who also searched for a companion to our Sun – a star dubbed Nemesis. The Nemesis is believed to have kicked an asteroid into the orbit of the Earth. The asteroid collided with the Earth and killed the dinosaurs. It has never been found though.

A radio survey of a giant molecular cloud filled with recently formed stars in the constellation Perseus was carried out by researchers, including those from University of California (UC) Berkeley in the US.

A mathematical model that can explain the Perseus observations only if all sunlike stars are born with a companion was also created by the team.

“We are saying, yes, there probably was a Nemesis, a long time ago,” said co-author Steven Stahler, researchers at UC Berkeley.

“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,” researchers said.

Stahler said these systems then either shrink or break apart within a million years. ‘Wide’ in this study means that two stars are separated by more than 500 astronomical units (AU). One AU is the average distance between the sun and Earth (about 150 million kilometres).

They sad that the Sun’s wide binary companion would have been 17 times farther from it than its most distant planet today – Neptune.

They said 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.

“Based on our simple model, we say that nearly all stars form with a companion,” said Sarah Sadavoy, from the Smithsonian Astrophysical Observatory in the US.

Stars are born inside egg-shaped cocoons called dense cores, which are sprinkled throughout immense clouds of cold, molecular hydrogen that are the nurseries for young stars.

Researchers mathematically modelled various scenarios to explain this distribution of stars, assuming typical formation, breakup and orbital shrinking times.

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They concluded that the only way to explain the observations is to assume that all stars of masses around that of the Sun start off as wide Class 0 binaries in egg-shaped dense cores, after which some 60 per cent split up over time.  The rest shrink to form tight binaries. 

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(With inputs from PTI)