Artist concept of Alpha Centauri Bb
Artist concept of Alpha Centauri Bb

If you’ve been keeping up on the now very frequent reports of new extrasolar planet discoveries, here’s a news flash: an Earth-sized exoplanet has been found orbiting the nearest star!

It’s called Alpha Centauri Bb and orbits one of the pair of main stars that make up the Alpha Centauri system, Alpha Centauri B. (I heard that if you mention a name three times, people will remember it, so there you are. Either that or Michael Keaton shows up wearing a lot of make-up.)

The Alpha Centauri system is famous for several reasons, some popular, some more esoteric. First and most famously, it is celebrated as the closest star to our solar system: 4.3 light years, or a mere 25 trillion miles. But the fact that it is actually a system of three stars complicates this distinction a bit.

The two main stars, Alpha Centauri A and B, orbit each other every 80 years at a mutual distance ranging from the sun-Saturn and sun-Pluto distances (roughly 3 billion and 4 billion miles, respectively). Alpha Centauri A is about 10% more massive than our sun, and B is about 10% less weighty. The pair’s combined luminosity and nearness in space make them the third brightest “star” in the night sky (from Earth they are seen as a single star).

The third star of the trio is Alpha Centauri C (aka Proxima Centauri). And though C is a red dwarf star and not visible to the unaided human eye, being a fifth of a light year closer to us than the A-B pair makes Proxima officially the closest star to our solar system. (Which is a bit ironic since it’s not naked-eye visible!)

The newly found planet, Alpha Centauri Bb, will not have an Earth-like environment to offer us. It is less than 4 million miles from its star and takes only 3.2 days to orbit it once. Its surface temperature is estimated to be 1200 degrees C. The planet is, however, very Earth-like in terms of its size: about 1.13 times the mass of the Earth.

Now the more esoteric claim to fame: Alpha Centauri was the fictional destination of the Space Family Robinson on the 60’s television show “Lost In Space“–in fact, it was the name used for the actual planet they were headed for. Alpha Centauri; Alpha Centauri Bb. Hmm.

Fifty years after the Robinson’s took off on their great misadventure, have we found the planet they were headed for? Probably not, considering Alpha Centauri Bb’s surface temperature would melt all of their ship’s aluminum fittings, but the find does demonstrate that planets are to be found around the nearest star, opening up the possibility for a more Earth-like landing site sometime in the future…if the Robinsons ever finally find their way to Alpha Centauri!

Found In Space: Exoplanet Alpha Centauri Bb 11 June,2013Ben Burress


Ben Burress

Benjamin Burress has been a staff astronomer at Chabot Space & Science Center since July 1999. He graduated from Sonoma State University in 1985 with a bachelor’s degree in physics (and minor in astronomy), after which he signed on for a two-year stint in the Peace Corps, where he taught physics and mathematics in the African nation of Cameroon. From 1989-96 he served on the crew of NASA’s Kuiper Airborne Observatory at Ames Research Center in Mountain View, CA. From 1996-99, he was Head Observer at the Naval Prototype Optical Interferometer program at Lowell Observatory in Flagstaff, AZ.

Read his previous contributions to QUEST, a project dedicated to exploring the Science of Sustainability.

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