Scientists discovered new five-planet system

NASA scientists discovered a fifth planet orbiting a star outside our own solar system and say the discovery suggests there are many solar systems that are just like our own, with planets orbiting sun.

The new planet is about 45 times much bigger than Earth and has an orbit of 260 days, but is a similar distance away from its sun, a star known as 55 Cancri, star 55 in the constellation Cancer. Orbiting a sun-like star 41 light years* away in that constellation, making it the first known planetary quintet outside our solar system, the astronomers said on Tuesday.

Four planets had already been seen around the star, but the discovery marks the first time as many as five planets have been found orbiting a solar system outside our own with its eight planets. "It's a system that appears to be packed with planets," said co-discoverer Debra Fischer, an astronomer at San Francisco State University.

It was detected after nearly two decades of observations by ground-based telescopes using the Doppler technique that measures a planet's stellar wobble. Life could conceivably live on the surface of a moon that might be orbiting the new planet, but such a moon would be far too small to detect using current methods, the astronomers said.

"The star is very much like our own sun. It has about the same mass and is about the same age as our sun," Fischer told reporters.

"It's a system that appears to be packed with planets."

It took the researchers 18 years of careful, painstaking study to find the five planets, which they found by measuring tiny wobbles in the star's orbit. The first planet discovered took 14 years to make one orbit.

The other planets in the 55 Cancri system were discovered between 1996 and 2004. The innermost planet is believed to resemble Neptune, while the most distant is thought to be Jupiter-like.

More than 260 planets have been identified outside our solar system, exoplanets or planets orbiting a star other than the sun. The 55 Cancri star holds the record for number of confirmed planets. Only one other star is known to have four planets, while several others have three or less.

"We can now say there are stars like the sun that have many worlds around them," said planetary scientist Jonathan Lunine of the University of Arizona, Tucson, who had no role in the discovery.

The latest discovery shows that our solar system is not unique, scientists said.

"It would be a little bit warmer than the Earth but not very much," said Jonathan Lunine, a planetary scientist at the University of Arizona.

The planet is 72 million miles from its star - closer than the Earth's 93 million miles, but the star is a little cooler than our own sun.

"If there were a moon around this new planet, it would have a rocky surface, so water on it in principle could puddle into lakes and oceans," said Geoff Marcy, an astronomer at the University of California, Berkeley.

But the moon would have to carry a lot of mass to hold the water, he said. Water is, of course, key to life.

"This discovery of the first-ever quintuple planetary system has me jumping out of my socks," Marcy added. "We now know that our sun and its family of planets is not unusual."

Marcy and other astronomers strongly believe that many stars are hosts to solar systems similar to our own. But small objects such as planets are very hard to detect.

Technology that would allow scientists to detect planets as small as Earth is decades away, the scientists agreed.

The researchers have been looking at 2,000 nearby stars using the Lick Observatory near San Jose, California, and the W.M. Keck Observatory in Mauna Kea, Hawaii.

They have posted images of what the planets may look like on the Internet at http://www.nasa.gov/audience/formedia/telecon-20071106/.

The inner four planets of 55 Cancri are all closer to the star than Earth is to the sun. The closest, about the mass of Uranus, zips around the star in just under three days at a distance of 3.5 million miles.

"When you look up into the night sky and see the twinkling lights of stars, you can imagine with certainty that they have their own complement of planets," said astronomer Geoff Marcy of the University of California, Berkeley, who was part of the research.


* A light-year being the distance light travels in one year - about 5.8 trillion miles.


Adapted from the news by Voanews





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