7 True Facts About the Bizarre Double-Star System Eta Carinae

The Homunculus Nebula looks alive. Its two lobes of gas, which resemble twin human hearts stuck artery to artery, stretch half a light-year each from its center. And they’re getting bigger all the time, swelling outward at 1.5 million miles per hour. If you could fly through them, on some Magic School Bus, you’d find two stars at their center—two huge stars, whipping around each other once every 5.5 years. When their orbits bring them close together, as they did in August 2014, the stars are only as far apart as Mars and the sun. During that close passage, and the two previous to that, astronomers peered deep into the heart of the Homunculus Nebula to find out about the stars that supply its blood. Here’s what they’ve learned about Eta Carinae—the name given to the pair of stars—and what its massive liveliness tells us about the rest of the ...