The Sun’s Ghostly Twin

Our Sun may have a long-lost twin. Not an identical twin, but a sibling formed from the same cloud of gas and dust. Astronomers suspect that many stars, including the Sun, are born in pairs—sometimes in wide orbits that eventually separate. A related but different idea, a hypothetical distant companion called “Nemesis,” was once blamed for mass extinctions on Earth, theorized to disrupt comets in the Oort Cloud every 26 million years. NASA’s WISE infrared survey found no sign of such a companion, but the idea lingers. After all, if our Sun was born with a twin, where did it go?