HARPs Calls The Tune… Earth-Sized Planet Found InSystem!
Ask anyone what the nearest star system to Earth is and you’ll get the answer – the Alpha Centauri system. It’s where the Robinson’s went, right?
Now ask them where to find an Earth-sized planet and you’ll get a variety of answers. Not any more. Thanks to the HARPS instrument on the 3.6-meter telescope at ESO’s La Silla Observatory in Chile, a new exoplanet has come to light… the lightest ever discovered around a Sun-like star and orbiting in the Alpha Centauri system!
Southern observers are quite familiar with the presence of Alpha Centauri. After all, it’s one of the brightest stars and one of the closest, too. This 4.3 light year distant triple star system has two companion stars very similar to the Sun with the third, a faint red star known as Proxima Centauri. For two hundred years astronomers have speculated there might be planets located around these stars, but could never prove their theories despite improvements in observing equipment. But then, there’s never been an instrument like HARPs before!
“Our observations extended over more than four years using the HARPS instrument and have revealed a tiny, but real, signal from a planet orbiting Alpha Centauri B every 3.2 days,” says Xavier Dumusque (Geneva Observatory, Switzerland, and Centro de Astrofisica da Universidade do Porto, Portugal), lead author of the paper. “It’s an extraordinary discovery and it has pushed our technique to the limit!”
How did they do it? Weebles wobble. By detecting a slight wobble in the motion of Alpha Centauri B, the researchers knew there had to be a planet creating a minute gravitational pull. Sure, the effect is slight – on around 51 centimeters per second – but this is a huge number when it comes to HARPs precision instrumentation. The star itself is incredibly similar to our own, just slightly smaller and only a bit less bright. The new exoplanet is assumed to be orbiting about six million kilometers away, less than Mercury’s distance. However, don’t forget this is a double star system! Alpha Centauri A keeps it hundreds of times further away, but would be an incredible sight in this newly discovered planet’s skies!
Coincidentally, the same team was also the first to discover an exoplanet around a Sun-like star seventeen years ago. Since that time, there has been more than 800 confirmed