Scientists find most Earthlike planet yet

By Ker Than

Staff writer

updated 9:53 a.m. ET April 25, 2007

An Earthlike planet spotted outside our solar system is the first found that could support liquid water and harbor life, scientists announced Tuesday.

Liquid water is a key ingredient for life as we know it. The newfound planet is located at the "Goldilocks" distance — not too close and not too far from its star to keep water on its surface from freezing or vaporizing away.

And while astronomers are not yet able to look for signs of biology on the planet, the discovery is a milestone in planet detection and the search for extraterrestrial life, one with the potential to profoundly change our outlook on the universe.

”The goal is to find life on a planet like the earth around a star like the sun. This is a step in that direction,” said study leader Stephane Udry of the Geneva Observatory in Switzerland. “Each time you go one step forward you are very happy.”

The new planet is about 50 percent bigger than Earth and about five times more massive. The new “super-Earth” is called Gliese 581 C, after its star, Gliese 581, a diminutive red dwarf star located 20.5 light-years away that is about one-third as massive as the sun.

Smallest to date
Gliese 581 C is the smallest extrasolar planet, or “exoplanet,” discovered to date. It is located about 15 times closer to its star than Earth is to the sun; one year on the planet is equal to 13 Earth days. Because red dwarfs, also known as M dwarfs, are about 50 times dimmer than the sun and much cooler, their planets can orbit much closer to them while still remaining within their habitable zones, the spherical region around a star within which a planet’s temperature can sustain liquid water on its surface.

Slideshow   Month in Space: Blasts from beyond See moonshadows on Saturn's rings, volcanoes on Earth and Mars and other out-of-this-world imagery from June 2009. more photos

Because it lies within its star’s habitable zone and is relatively close to Earth, Gliese 581 C could be a very important target for future space missions dedicated to the search for extraterrestrial life, said study team member Xavier Delfosse of Grenoble University in France.

“On the treasure map of the universe, one would be tempted to mark this planet with an X,” Delfosse said.

Two other planets are known to inhabit the red dwarf system. One is a 15 Earth-mass “hot-Jupiter” gas planet discovered by the same team two years ago, which orbits even closer to its star than does Gliese 581 C. Another is an 8 Earth-mass planet discovered at the same time as Gliese 581 C, but which lies outside its star’s habitable zone.

Possible waterworld
Computer models predict Gliese 581 C is either a rocky planet like Earth or a waterworld covered entirely by oceans.

“We have estimated that the mean temperature of this super-Earth lies between 0 and 40 degrees Celsius [32 to 104 degrees Fahrenheit], and water would thus be liquid,” Udry said.

The scientists discovered the new world using the HARP instrument on the European Southern Observatory 3.6 meter telescope in La Sille, Chile. They employed the so-called radial velocity, or “wobble,” technique, in which the size and mass of a planet are determined based on small perturbations it induces in its parent star’s orbit via gravity.

Udry said there was a fair amount of time between the calculation of Gliese 581 C’s size and the realization it was within its star’s habitable zone. “That came at the end,” Udry said.

When it did hit him, Udry knew he would be spending time fielding phone calls from the media. “You right away think about the journalists who will like it very much,” he told Space.com.

MORE FROM SPACE

Space Section Front

New moon vistas revealed Astronaut taking Twitter to space en Español How Martian clouds create snowfall Scientists explain Martian soil surprises Drink up! Guinness offers seat on a spaceliner Inflatable tower may offer easier access to space Shuttle Endeavour OK’d for liftoff after tests Gravity's imprint sought in big bang’s glow World’s largest commercial satellite in orbit   Month in Space: Blasts from beyond Space Section Front   Add Space headlines to your news reader: