Potentially habitable planet found
A rocky planet with the potential to support liquid water — and therefore the potential to support life — has been found orbiting a sun-like star near our solar system.
The planet, known as HD 85512 b, is among 50 planets outside our solar system, called exoplanets, recently discovered using the HARPS instrument on the 3.6-metre telescope at La Silla Observatory in Chile, operated by the European Southern Observatory.
The findings were announced Monday at a conference on Extreme Solar Systems in Grand Teton National Park, Wyo., by an international team led by Michel Mayor at the University of Geneva in Switzerland. They will be published as three articles in an upcoming issue of the journal Astronomy & Astrophysics.
HD 85512 b has a mass about 3.6 times greater than the Earth's, making it a class of rocky planet called a "super-Earth." Such planets don't exist in our solar system, but appear to be common around other stars. The planet orbits the star HD 85512 in the southern constellation Vela (The Sail), which is only visible at latitudes below 30 degrees north. The orbit grazes the edge of the habitable zone around its star — the band around the star where the temperature could potentially allow liquid water to exist if conditions are right.
The new exoplanet was discovered during a survey that focused on 10 nearby stars similar to the sun. The survey found more than 50 new planets around them, including 16 super-Earths, defined as being more massive than the Earth, but less than 10 times more massive.
Of the 16 super-Earths, five were less than five times more massive than the Earth, including HD 85512 b.
"These planets will be among the best targets for future space telescopes to look for signs of life in the planet's atmosphere by looking for chemical signatures such as oxygen," said Francesco Pepe, an astronomer at the Geneva Observatory in Switzerland who was the lead author on one of the papers describing the findings.
The technique used by the HARPS instrument is called the radial velocity technique or Doppler spectrometry. It measures small changes in the movement of stars caused by the tug of a nearby planet's gravity. The changes result in a Doppler shift — small shifts in the colour of light — as the light-emitting star moves toward or away from the Earth.
Over 600 exoplanets and more than 1,000 other potential exoplanets have been discovered using HARPS and NASA's Kepler telescope. But only one other planet has been found on the edge of the habitable zone of a star.
That planet, called Gliese 581 d, is another super-Earth discovered using HARPS in 2007. Scientists announced another planet in the same system called Gliese 581 g in 2010 that appeared to be right in the middle of the habitable zone. However, that planet was later shown not to exist — scientists had misinterpreted the data.