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Proxima Centauri Planets

September 11, 2015

If humanity ever launches a starship, the most reasonable destination is the closest one: the star Proxima Centauri, which is just four-and-a-quarter light-years away. Unfortunately, though, there’s not much to see when it gets there. Proxima is a tiny stellar ember known as a red dwarf. And so far, searches for planets around the star have turned up empty.

Planet searchers have kept an eye on Proxima Centauri for decades. They’ve used Hubble Space Telescope, for example, to look for changes in its location caused by the pull of an orbiting planet. They’ve also measured the star’s velocity toward and away from us, hoping to discover a planet through its gravitational tug on the star. But those searches have found nothing. That means that Proxima has no close-in planet more massive than Neptune, one of the giants of our own solar system.

A more recent search looked at how a planet tugs the star sideways, across our line of sight. This technique is more sensitive to planets that are far away from the star. But this attempt didn’t find any planets, either.

Together, the searches mean that Proxima Centauri has no planets as massive as Jupiter in orbits of less than than 12 years — the length of our Jupiter’s orbit around the Sun.

That may mean that Proxima Centauri has no planets at all. And if it does have planets, they’re either smaller than Jupiter or they orbit far from the star — or perhaps both.


Script by Ken Croswell, Copyright 2015

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