[T]oday a European planet-hunting team announced their discovery of an alien world about the same mass as Earth. This alone would be noteworthy, for of all the “exoplanets” now known beyond our solar system, only a very few, and very recently, have been shown to at all resemble our own. But there is more to the story. This particular exoplanet resides in a three-day orbit around the dusky orange star Alpha Centauri B, a member of the Sun’s closest neighboring stellar system. There are two other stars in the system as well, the yellow Sun-like star Alpha Centauri A and the red dwarf star Proxima Centauri.
At a distance of just over 4.3 light years, the stars of Alpha Centauri are only a cosmic stone’s throw away. To reach Alpha Centauri B b, as this new world is called, would require a journey of some 25 trillion miles. For comparison, the next-nearest known exoplanet is a gas giant orbiting the orange star Epsilon Eridani, more than twice as far away. But don’t pack your bags quite yet. With a probable surface temperature well above a thousand degrees Fahrenheit, Alpha Centauri B b is no Goldilocks world. Still, its presence is promising: Planets tend to come in packs, and some theorists had believed no planets at all could form in multi-star systems like Alpha Centauri, which are more common than singleton suns throughout our galaxy. It seems increasingly likely that small planets exist around most if not all stars, near and far alike, and that Alpha Centauri B may possess additional worlds further out in clement, habitable orbits, tantalizingly within reach.
Australians (and other people of low enough latitudes) will know the Centauri star system as the left-hand (eastern) pointer star associated with the Southern Cross constellation. And speaking of constellations, Lee Billings points out the breath-taking fact that in galactic terms, the newly-discovered exoplanet “is so very near our own that its night sky shares most of Earth’s constellations” – excepting the constellation Cassiopeia, which would gain a sixth star, six times brighter than the other five: our own Sun.
Some of the other interesting tweets seen shortly after the announcement:
At 1:93,000,000 scale (1 mile per 1 Astronomical Unit) the Sun-Pluto distance is 40 miles. Alpha Cen would be distance from Earth to Moon.