Stolen World: 'Planet 9' Likely Came from Another Star

There may be an alien planet lurking within Earth's own solar system. "It is almost ironic that while astronomers often find exoplanets hundreds of light-years away in other solar systems, there's probably one hiding in our own backyard," study lead author Alexander Mustill, an astronomer at Lund University in Sweden, said in a statement. Earlier this year, astronomers Konstantin Batygin and Mike Brown, both of the California Institute of Technology in Pasadena, announced the possible existence