Astronomers Have Discovered a Planet Orbiting the Closest Star to our Solar System!
From ESO (The European Southern Observatory):
Astronomers using ESO telescopes and other facilities have found clear evidence of a planet orbiting the closest star to the Sun, Proxima Centauri (a red dwarf star, too faint to be seen with the unaided eye, 4.2 light-years from the Solar System). The long-sought world, designated Proxima b, orbits its cool red parent star every 11 days and has a temperature suitable for liquid water to exist on its surface. This rocky world is a little more massive than the Earth and is the closest exoplanet to us — and it may also be the closest possible abode for life outside the Solar System.
The paper describing this milestone finding is published in the journal Nature.
During the first half of 2016 Proxima Centauri was regularly observed with the HARPS spectrograph on the ESO 3.6-metre telescope at La Silla in Chile and simultaneously monitored by other telescopes around the world [1]. This was the Pale Red Dot campaign, in which a team of astronomers led by Guillem Anglada-Escudé, from Queen Mary University of London, was looking for the tiny back and forth wobble of the star that would be caused by the gravitational pull of a possible orbiting planet [2].
Phil Plait explains further in his article (read all here):
Because it’s the closest star to the Sun, astronomers have looked at it for decades to see if there’s any evidence of a planet. There have been false alarms over the years, all eventually shown to be errors.
But this time it looks like it’s very much real. The difference is the quality of data, because our technology and techniques have improved mightily recently. Using two different cameras on two different telescopes, the astronomers divided the light from Proxima into a spectrum. They looked for subtle and periodic changes in the spectrum that would be due to a planet orbiting the star. As the planet moved, it would tug on the star;Proxima would make a little circle as the planet made a bigger one. This creates a Doppler shift in the spectrum, which in principle can be measured.
The faster the planet orbits, the bigger the shift, and usually the easier it is to detect. The motion Proxima b imparts on its star is very small, just one or two meters per second.* That’s very hard to detect.
But the eyesight of the cameras was sharp, and the ability of the astronomers to tease out the signal greater.
He also gives a down-to-earth perspective:
Mind you, we know nothing of its composition, or even its size. It may be completely uninhabitable, or it might be Eden. There’s no way to know. So be cautious here: It’s likely to be Earth-size, but we don’t know if it’s Earth-like.
Either way, it’s more than 40 trillion kilometers away, so we’re not going there any time soon. The fastest spacecraft we’ve ever launched would take many tens of thousands of years to get there. Don’t pack your underthings just yet.
Still, this is terribly, terribly exciting. We’ve only known for sure about the existence of exoplanets—worlds orbiting alien suns—since 1992. The first found were orbiting a dead star, a pulsar. The first planet orbiting a Sun-like star wasn’t found until 1995, and in the next two decades we built telescopes dedicated to looking for them, and as of today we know of over 3,000 such strange, new worlds.
Quite a few are Earth-size, and fewer possibly Earth-like. Still, we can make estimates that there are billions of Earth-size planets in the galaxy.
And now we know that it’s possible that the nearest one is, on a cosmic scale, right next door.
*Correction: it was originally misstated that this was the speed the planet goes around the star, not the speed of the star itself.
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