Wednesday, October 17, 2012

Planet Found in Closest Star System to the Sun

Big News: Nearest Star System Has a Planet

European astronomers have announced a science-fiction dream come true. A planet is orbiting one of the stars in the nearest star system to the Earth -- Alpha Centauri. This system consists 
of two stars orbiting a common center in 80 years (and perhaps a third star, even further out.)

The smaller star of the main pair, called "Alpha B" is the one where a planet has been found. Astronomers use the "wiggle method," where they detect the pull of the planet by changes in the motion of the STAR. (The star is bright and can be seen, while the planet is small and dim and lost in the star's glare. So we had to find the planet by the pull of its gravity on its parent star.) It took FOUR years of careful measurement to tease out the tiny wiggle caused by the planet's pull!

The planet is small (roughly like the Earth) but much closer in than we are to the Sun. This new planet (for now called "Alpha Bb" -- we astronomers are NOT good at romantic names!) takes only 3 days to orbit its parent star. That means it is only a little more than 3 million miles away from the star (while the Earth is 93 million miles from the Sun.) The planet must be intensely hot and hardly a place to build a resort for space travelers.

Still, this is amazing and wonderful news for several reasons:

1. It's great to have a planet in the star system next door (and that system may yet reveal other planets too.) Alpha Centauri is about 4 lightyears away.

2. It's great that our instruments can make so precise and tiny a measurement at star distances (the change in the star's motion due to the planet's pull is only about 1 mile per hour) and this means other small planets may also be found using the wiggle method.

3. With over 842 planets now known for sure orbiting 664 other stars (and thousands more suspected), this discovery is one more piece of evidence that planets can exist not just among single stars like the Sun, but in systems of stars too.