We’ve seen ourselves in the heavens. A giant spiral galaxy 180 million light years from Earth not only resembles the Milky Way but also boasts a pair of interacting galaxies that look like our galaxy’s two brightest satellites.
At least 50 galaxies orbit the Milky Way. Most have run out of gas because they’ve spent more time close enough to our galaxy for it to steal their gas. But two of the nearest satellites – the Large and Small Magellanic Clouds – have been in our neighbourhood for less time, and still possess lots of gas that spawns new stars. The two galaxies are respectively 160,000 and 200,000 light years from us and 75,000 light years from each other.
This arrangement is rare. Most giant galaxies don’t have even one star-making companion nearby, let alone two. That’s probably because a giant galaxy strips small neighbours of gas, thwarting their ability to make new stars.
Sanjaya Paudel and Chandreyee Sengupta at Yonsei University in Seoul, South Korea, looked through images of nearly 20,000 small galaxies for a pair that resides near a giant galaxy. “It’s obviously very difficult,” says Paudel.
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