Exploring our Universe

Scientists use telescope in Chile to discover nearest exoplanet

Astronomers in the Atacama Desert have found the closest planet outside of our Solar System - and unlike its predecessors, it has a mass similar to Earth’s. 

Monday, October 22, 2012  
Artist’s impression shows the exoplanet orbiting the star Alpha Centauri B, a member of the triple s Artist’s impression shows the exoplanet orbiting the star Alpha Centauri B, a member of the triple star system that is the closest to Earth. Image by ESO/L. Calçada/Nick Risinger (skysurvey.org)

Astronomers from the European Southern Observatory (ESO) announced an unprecedented discovery made in Chile last week: an exoplanet with a mass similar to that of Earth is orbiting a star in our closest star system neighbor, Alpha Centauri.  


While there are currently over 800 confirmed exoplanets in the Universe, most are much bigger than Earth, and many are as large as Jupiter. This exoplanet, however, is the lightest ever discovered around a star like our Sun, and by far the nearest at only 4 light-years from Earth, according to ESO.


The discovered exoplanet’s orbit is very close to its star Alpha Centauri B (even closer than the distance between Mercury and the Sun), and therefore too hot for life as we know it. But it is conceivable that other exoplanets could fall within a habitable zone, according to ESO.


Astronomers have been studying the exoplanet for over four years using the HARPS instrument on the 3.6-meter telescope at the La Silla Observatory. HARPS detected the planet by tracking the tiny wobbles in the motion of Alpha Centauri B, which are created by the gravitational pull of the orbiting exoplanet. The rate of the star’s wobble is tiny - only about 20 inches (51 cm) per second, or about the speed of a baby crawling - but the instrument is able to track the movement with incredible precision.


According to ESO Astronomer Dr. Joe Liske, host of ESO’s news video podcast, this exoplanet discovery is exciting because it opens doors to the possibility that Earth-like planets exist elsewhere in the universe.


“The fact that there is an Earth-sized planet in our nearest star system gives hope that they are prevalent. If you know the closest star has this type of a planet, it makes us hopeful that a large fraction of stars could also,” Dr. Liske told This is Chile.


The discovery so “close” to Earth has also excited scientists by raising the possibility of one day - in the distant future - sending a probe to the planet to collect data straight from the source. While it currently takes four years just to receive a photograph from Alpha Centauri B, the star’s relative proximity to Earth created a thought-provoking hypothetical nonetheless.


It’s conceivable that we could send something there. We might not have the technology now, but it would be conceivable,” said Dr. Liske.  “This was probably the first time, at least for me, that I began to think that it actually might make sense to send a probe to that distance.” 

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