Astronomers have found a New Planet orbiting closest Star to the Sun!
AstronomerWizards have found a new planet orbiting the closest star to us, Proxima Centauri. This is pretty fantastical news.
There’s no other way to phrase it. This is HUGE news: Astronomers have found a planet orbiting the Proxima Centauri, the closest star to the Sun!
Before I get into details, let me sum up what we know:
The planet, called Proxima Centauri b or just Proxima b (exoplanets are given their star’s name plus a lower case letter in order of discovery, starting with “b”), orbits Proxima every 11.2 days. It has a mass of no less than 1.3 times the Earth’s, so if it’s rock and metal like Earth it’s only a bit bigger. It’s a mere 7.3 million kilometers from the star — a lot closer than Earth’s distance from the Sun of 150 million km! — but Proxima is so faint and cool it receives about two-thirds the amount of light and heat the Earth does. That means that it’s in Proxima’s habitable zone: It’s possible (more or less) that liquid water could exist on its surface.
There’s some backstory here, and it’s very cool. Proxima Centauri is a red dwarf, only 0.14 times the diameter of the Sun and 0.12 times its mass. Its surface temperature is much lower, so it’s cool and red, what we call a red dwarf. It orbits a binary star called Alpha Centauri, made of two stars more similar to the Sun (so the whole system is a trinary star). Proxima is pretty far out from the pair, about 0.1 light years or so (a trillion kilometers), about 200 times farther than the distance of Neptune from the Sun. So it’s nearly out by itself in space, barely bound to the binary.
The Alpha Centauri binary is easily visible from Earth’s southern hemisphere, though they look like one star at their distance of about 4.3 light years, and are among the brightest stars in the sky. Proxima, even though it’s closer to us, is so intrinsically dim that you need a good pair of binoculars to see it at all.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 showing many individual colors. 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.