Many sunlike stars are eerie clones, but ours is an individual. A study of solar twins reveals that the sun’s chemical makeup is surprisingly different from that of its nearby peers, while those stars are almost identical to one another. Since a star and its planets are made from the same materials, that may mean the exoplanets orbiting those stars come in just a few flavors. It also could point to a new way to discover stars with solar systems more like ours.
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“Past studies have said that there is a lot of diversity from star to star, so there should be a lot of diversity among planets,” Bedell says. “We’re seeing a lot of the same.”
But not when it comes to the sun. The team found that the sun’s elements come in subtly different proportions. For example, the sun is missing about four Earth masses worth of rocks and metals — the very elements that the planets are made of. That result could be because of the solar system: The elements are missing from the sun because they’re locked up in the planets, Bedell says. There’s another, less savory possibility: The other stars might contain more rocky elements because they once had planets, and ate them.
Only a minority — 7 to 20 percent — of the stars measured by Bedell’s team matched the sun. No planets have been found orbiting those stars. “Of course that doesn't mean that they don't have planets, just that we can't see them yet,” Bedell says. Searching for other stars that share this shortage of rock and metal elements could help astronomers find other solar systems like our own.
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