Sun’s missing twin may have wiped out the dinosaurs

Scientists think “brother” star forced an asteroid towards Earth before escaping Solar System

THE Solar System once had two suns, scientists believe, and one of them may have helped wipe out the dinosaurs.

A theoretical physicist at the University of California and an astronomer from Harvard University have discovered that most stars are born with a “brother” and our own Sun is likely to be no exception. In fact, this twin, which is named a Nemesis, may have been responsible for forcing an asteroid into Earth’s orbit, leading to the extinction of the dinosaurs.

In the Eighties, two palaeontologists from the University of Chicago suggested that the regular rate of mass ex- tinctions on Earth – every 26million years – was caused by a mysterious “second Sun”. But, despite years of searching, nobody could ever find it.

Now the new study suggests that the Sun did have a companion star billions of years ago, but it probably escaped the Solar System and is now lost in the Milky Way.

“We are saying, yes, there probably was a Nemesis, a long time ago,” said study author Prof Steven Stahler, of UC Berkeley. “Astronomers looked hard for it, back in the Eighties, but it was never found, and the search was abandoned. It was supposed to send comets crashing into the Earth, thus explaining mass extinctions, like those of the dinosaurs. It would now be thousands of light years distant, and impossible to find.” Scientists believe the Nemesis must have existed after studying a giant cloud of recently formed stars in the constellation Perseus. Last year, astronomers completed a survey of the stellar nursery, which is about 600 light years from Earth, using the Very Large Array, in New Mexico, and Hawaii’s James Clerk Maxwell Telescope.

They found 55 baby stars in 24 multiple-star systems, and all but five of them had companion stars. The team concluded that all stars like the Sun start off with a twin, and some 60 per cent split up over time. “The idea that many stars form with a companion has been suggested before, but the question is, how many?” said Sarah Sadavoy, a Nasa Hubble fellow at Harvard’s Smithsonian Astrophysical Observatory. “Based on our simple model, we say that nearly all stars form with a companion.”

Prof Stahler added: “Perhaps Sun II has a small planet whose inhabitants are also wondering about their own origins.” The research was published in Monthly Notices of the Royal Astronomical Society.