Every now and then someone tries to trip me up with that old trick question, "What's the closest star to Earth?"
"Hmm," I reply in mock contemplation. "Is it the Sun?"
This little exchange underscores how we've come to regard old Sol as a one-of-a-kind star. But now two astronomers think they've found the closest thing yet to the Sun's twin. It's not some long-lost, separated-at-birth companion, but rather a 9th-magnitude blip in the constellation Draco that's about 200 light-years away.It's designated HIP 56948, and it's gotten a lot of attention recently from Peruvian astronomers Jorge Melendez (Australian National University) and Ivan Ramirez (University of Texas, Austin). They used the 2.7-meter telescope at McDonald Observatory to study the star, concluding that HIP 56948 is a dead ringer for our Sun not only in terms of its mass and temperature but also its composition.
Three other stars 18 Scorpii, HD 98618 (in Ursa Major), and HIP 100963 (in Vulpecula) are "solar twins" in many ways. But they all contain several times more lithium than our Sun does. HIP 56948, by comparison, matches the Sun's lithium abundance quite well.
A star so very like our own would seem to be a good candidate to look for planets like our own. Alas, Bill Cochran (also at UT Austin) has already found that HIP 56948 has no large, close-in planets comparable to Jupiter. Earth-size worlds may still exist there, but we don't yet have the technology to detect them.