New Earth-Like Planet
Tuesday, November 06, 2007
New planet 'may be home to aliens'
Excited astronomers have discovered a new planet that could be home to alien life, they revealed tonight. The world is orbiting a nearby star like the Sun in its so-called "habitable zone" - just the right distance for liquid water to exist.
A Nasa artist's impression of the 55 Cancri solar ystemIt is the fifth planet to be identified in orbit around the star 55 Cancri, a star very similar in type and age to our own Sun, making it a virtual twin of our own solar system.
The star, which is dimly visible to the naked eye in the constellation of Cancer, now holds the record for the number of worlds in orbit, after our own Sun. It lies just 41 light-years away - right on our cosmic doorstep.
Scientists said the new planet is 45 times the mass, or size of the Earth, and has a year 260 days long - the time it takes to orbit 55 Cancri. It was found by measuring the tiny wobble it causes to the star as it orbits. Detecting this was a triumph for the astronomers and took them 18 years of study from Lick Observatory, California, because it had to be separated from the effects of the other planets.
The planet is 72.5 million miles from 55 Cancri, a little less than the distance of the Earth from the Sun, but at an ideal distance for the warmth that life as we know it would need to exist. Computers had previously identified the star as an ideal candidate to house Earth's twin.
Geoff Marcy, of the University of California, said last night: "The discovery has me jumping out of my socks. We now know that our own Sun and its family of planets is not unusual."
He said that if there is a moon going around this new planet, it would have a rocky surface. Water could form lakes or seas and produce the conditions for life to begin. But he added: "Then all bets are off as to how life could evolve on that moon."
Fellow discoverer Debra Fischer, of San Francisco State University, said she expected that other Earth-like planets could exist in the star's habitable zone. She said: "I bet that gap is not empty."
She added: "55 Cancri is very much like our own sun. It is about the same size and the same age. It is a solar system that is packed with planets. It has profound implications for how we search for Earth-like planets."
She went on: "The gas-giant planets in our solar system all have large moons. If there is a moon orbiting this new, massive planet, it might have pools of liquid water on a rocky surface."
In April, astronomers revealed they had discovered a planet resembling Earth in the habitable zone of a dwarf planet called Gliese 581 in the constellation of Libra.
Nasa associate administrator Alan Stern said: "It is amazing to see our ability to detect extrasolar planets growing. We are finding solar systems with a richness of planets and a variety of planetary types comparable to our own."
Answering questions, Debra Fischer said the new planet was more massive than Uranus or Neptune but less massive than Saturn, "so we don't know what it will look like."
Geoff Marcy said that, although it was speculative to say there were moons in orbit around the new planet, there were moons around ALL the giant planets in our own solar system.
He felt that, if the planet was like one of the giant planets in our solar system, then it was unlikely to be home to life itself, but conditions on one of its moons could be suitable.
Water has already been discovered a steam in the atmosphere of another giant planet beyond the solar system. And last month, results from the Spitzer space telescope revealed that a planet like Earth could be forming around a further star.