The Sciences

Most Stars in the Universe Host an Alien Planet

D-briefBy Bill AndrewsMar 4, 2014 11:30 PM

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Fans of exoplanets have had an exciting few days. First the long-awaited Kepler results were announced

, confirming over 700 new worlds outside our solar system. Exciting! That was tempered just a day later, however, by the news

that many of the “super earths” astronomers have discovered over the years — worlds larger than Earth, but smaller than Neptune — may in fact be inhospitable, even within their stars' habitable zones. But the latest exoplanet news buoys hopes of off-Earth habitability: a new study indicates that potentially habitable exoplanets are much more common that we’d thought.

The Odds Are Ever in Your Favor

The study authors, an international team of astronomers, combined and analyzed existing data from two planet surveys run by the European Southern Observatory: HARPS

(High Accuracy Radial Velocity Planet Searcher) and UVES

(Ultraviolet and Visual Echelle Spectrograph). By applying advanced statistical techniques to the data, the researchers discovered that a specific kind of star called a red dwarf is extremely likely to host at least one low-mass exoplanet (less than 10 times Earth’s mass). Scientists had expected planets to be plentiful throughout the cosmos, but at least one around every red dwarf turns out to be quite a pleasant surprise, since red dwarfs are particularly abundant — some estimates say at least three quarters of all the stars in the universe are red dwarfs. But that’s not all: It also turns out that nearly a quarter of low-mass, red dwarf exoplanets orbit within their star’s habitable zone. So, basically, if you pick 16 random stars, odds are that about 12 should have at least one low-mass planet in orbit, and three of those should be potentially habitable. Not bad, considering exoplanets were still purely hypothetical just 25 years ago. The study

is forthcoming in the Monthly Notices of the Royal Astronomical Society.

Bonus Exoplanets

As if that weren’t enough, the paper also announced the discovery of 8 new exoplanets (3 of them in their suns’ habitable zones). All orbit red dwarfs relatively nearby Earth, 15 to 80 light-years from the sun, and have orbital periods (i.e., years) ranging from two weeks to nine years. The study also confirmed the existence of two previously suspected exoplanets, and announced 10 new possible planets that need more study before they can be confirmed. All of which points to a fruitful new focus for exoplanet hunters. With their increasingly powerful instruments and analyzing techniques, astronomers' attention to red dwarf systems is sure to go up, along with the official exoplanet count. And, while these findings don't necessarily guarantee we'll end up finding a habitable planet, in a place as big as space, it always helps to know where to look. Image credit: D. Aguilar/Harvard-Smithsonian Center for Astrophysics

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