October 16 – Almost Home

Today’s factismal: The closest known extrasolar planet is Alpha Centauri Bb, a mere 4.4 light years away!

There’s an old astronomy joke that goes “What is the name of the closest star?” Ask that of most people and they will say “Alpha Centauri”; of course they would be wrong (the correct answer is “Sol” or “our Sun”). But there is a newer joke that just became possible a year ago; it asks “What is the name of the closest Earth-like planet?” Though the correct answer is “Terra”, “Tellus”, “Dirt”, or “Earth” (they all mean the same thing), the best answer is “Alpha Centauri Bb”.

That’s because astronomers have discovered a planet just slightly larger than Earth (1.13 times our mass, 1.04 times our size) that is orbiting the second brightest star in the Alpha Centauri system. The three stars that make up Alpha Centauri are a bit strange; the two brightest (A and B) orbit each other at a distance ranging from that of Saturn to that of Pluto  while the dimmest of the three (Proxima centauri) orbits the AB pair at what would be the distance of our Oort cloud (home of the comets). Using highly tuned spectroscopes, the astronomers were able to sort out a slight shift in the light from Alpha Centauri B that indicated a planet which they gave the designation of Alpha Centauri Bb.

An artist's deception of what the Alpha Centauri Bb system might look like (Image courtesy ESA)

An artist’s deception of what the Alpha Centauri Bb system might look like
(Image courtesy ESA)

Of course, there is some skepticism in the scientific community over whether or not Bb actually exists (hey, we’re scientists; skepticism is just what we do), especially given that no-one has observed Bb passing across the face of Alpha centauri B. However, that just means that we’re spending a lot more time watching that part of the skies right now. If you’d like to join in on the fun but don’t happen to have a 30 meter telescope in your backyard, then why not become a Planet Hunter? Using Keppler data, you’ll be able to discover planets of your very own!
http://www.planethunters.org/

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