Artist's impression of the newly discovered, water-rich super-Earth.
Credit: David A. Aguilar, CfA
PARIS: An Earth-like planet found orbiting a nearby star is rich in water - a major step forward in the search for worlds like our own, U.S. scientists say.
The so-called "super-Earth" is about 42 light years away in another solar system and has a radius nearly 2.7 times the Earth's, according to the researchers from the Harvard-Smithsonian Centre for Astrophysics (CfA) in Cambridge.
The discovery of the planet, called GJ 1214b, represents a "major step forward" in the search for worlds similar to our own, added the University of California's Geoffrey Marcy in a commentary. Both papers were published yesterday in the British journal Nature.
Water world
The "newfound world" is too hot to sustain life as we know it, according to the researchers. However, its density suggests that it "is composed of about three-fourths water and other ices and one fourth-rock," they said.
The planet's temperature is estimated at between 280 and 120 degrees Celsius with a host star about one-fifth the size of the Sun.
"Despite its hot temperature, this appears to be a water world," said Zachory Berta, a graduate student who first spotted hints of the planet's presence. "It is much smaller, cooler and more Earth-like than any other known exoplanet," he added, referring to planets outside our solar system.
Berta said some of the water would likely be in the crystalline form that exists at pressures greater than 20,000 times Earth's sea-level atmosphere.
Tantalising atmosphere
The new planet's temperature is much lower than that of the only similar discovery, called CoRoT-7b, which orbits a much hotter star, the scientists said.
CoRoT-7b has a density close to that of the Earth (5.5 grams per cubic centimetre) and seems to be rocky, while the new discovery appears to be much less dense (1.9 g/cm3).
"To keep the planet's density that low requires that it contains large amounts of water," said Marcy. "It must contain a huge amount of water, roughly 50 per cent by mass."
"There are also tantalising hints that the planet has a gaseous atmosphere," said the researchers. The "wild card" is the make-up of gases on the planet.
The planet orbits every 38 hours around a small, faint star that was first spotted by eight ground-based telescopes no larger than those used by amateur astronomers. Its relative closeness makes it possible to study the planet to determine its atmosphere.
"That will make it the first super-Earth with a confirmed atmosphere - even though that atmosphere probably won't be hospitable to life as we know it," said David Charbonneau who heads the research team.
"life as we know it"
It may not be able to sustain "life as we know it", but it's being a bit naive to assume that nothing lives in that temperature range. We see it here, after all, in some of those most extreme areas on the planet. Also, is that surface temperature? I would imagine that if it is mostly water, there'd be PLENTY of marine life if the planet is any decent age at all. The higher temperatures would speed up the process of evolution, after all.