Earth-like Planet detected in our Neighbourhood
Alpha Centauri system is made up of three stars: a red dwarf named Proxima, and two stars very much like our own sun, imaginatively named Alpha Centauri A and B. It’s already famed in sci-fi, but just recently astronomers have discovered something that will make any space-lover swoon: a planet orbiting Alpha Centauri B. This exoplanet is 1.13 times the mass of Earth, but that’s where the similarities end: while Earth orbits at a distance of 150 million kilometres from its sun, “Alpha Centauri Bb” orbits in a scorching hot zone just six million kilometres from its star—its surface could even be covered with molten rock. The planet is definitely not in the Goldilock’s Zone, so it does not contain liquid water and therefore is unlikely to harbour life as we know it. Still, it’s an amazing discovery for several reasons. The method with which the planet was detected is groundbreaking: planets don’t orbit a stationary star, but in fact the planet and star orbit a common centre of gravity, which means the star moves in miniscule amounts. Alpha Centauri B constantly wobbles as the planet orbits around it and exerts a gravitational tug, but this wobble is tiny—no more than 1.8 k/ph—so for us to detect it is phenomenal. More than 450 observations were made over four years in order to be sure, and the discovery marks the highest precision ever achieved using this method of detection. Even more exciting is the fact that Alpha Centauri Bb it’s the closest known exoplanet to Earth, at only 4.3 lightyears away. In cosmic terms, that’s just next door. Statistically, low-mass planets are formed in multi-planetary systems, so its mere existence suggests that Alpha Centauri holds even more undiscovered planets—and perhaps some formed in habitable zones.
(Artist’s Impressions Credit: 1, 2)