For decades, some scientists have speculated that the sun has a companion whose gravitational tug periodically jostles comets out of their normal orbits, sending them careening toward Earth. The resulting impacts have caused mass extinctions, the thinking goes, which explains the putative star's nickname: Nemesis.
Now, a new study reports that almost all sun-like stars are likely born with companions, bolstering the case for the existence of Nemesis.
"We are saying, yes, there probably was a Nemesis, a long time ago," study co-author Steven Stahler, a research astronomer at the University of California, Berkeley, said in a statement.
But the new results don't paint Nemesis as a murderer: The sibling star probably broke free of the sun and melted into the Milky Way galaxy's stellar population billions of years ago, study team members said.
Comment: Others do not believe Nemesis merely "melted" in to the Milky Way galaxy. And with good reason: