For the first time, astronomers have discovered a planet outside our solar system that is potentially habitable, with Earth-like temperatures, a find researchers described on Tuesday as a big step in the search for life in the universe.
The planet is just the right size, might have water in liquid form and -- in galactic terms -- is relatively nearby at 193 trillion kilometers away. But the star it closely orbits, a "red dwarf," is much smaller, dimmer and cooler than our sun.
Much is still unknown about the new planet, which could still be deemed inhospitable to life after more reached. It is also worth noting that scientists' requirements for habitability include a size relatively similar to Earth's with temperatures that would permit liquid water. Under these requirements, Mars would also be classified as habitable.
"It's a significant step on the way to finding possible life in the universe," said University of Geneva astronomer Michel Mayor, one of 11 European scientists on the team that found the planet.
"It's a nice discovery," he said. "We still have a lot of questions."
The results of the discovery have not been published but have been submitted to the journal Astronomy and Astrophysics.
Alan Boss, who works at the Carnegie Institution of Washington where a US team of astronomers competed in the hunt for an Earth-like planet, called the discovery "a major milestone in this business."
The planet was discovered by the European Southern Observatory's telescope in La Silla, Chile, which has a special instrument that splits light to find wobbles in different wave lengths.
Those wobbles can reveal the existence of other worlds.
What they revealed is a planet circling the Gliese 581 red dwarf star. Red dwarfs are low-energy, tiny stars that give off dim red light and last longer than stars like our sun. Until a few years ago, astronomers didn't consider these stars as possible hosts of planets that might sustain life.
The discovery of the new planet, named 581 c, is sure to fuel studies of planets circling similar dim stars. About 80 percent of the stars near Earth are red dwarfs.
The new planet is about five times heavier than Earth. Its discoverers are not certain if it is rocky like Earth or if its a frozen ice ball with liquid water on the surface.
If it is rocky like Earth, which is what the prevailing theory proposes, it has a diameter about one-and-a-half times bigger than our planet. If it is an iceball, as Mayor suggests, it would be even bigger.
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