Earth-sized planet might be found in outer solar system

Astronomers have suggested that a planet roughly the size of Earth could be tracing a vast, elliptical orbit at the outer edge of our solar system.

Washington, March 18 : Astronomers have suggested that a planet roughly the size of Earth could be tracing a vast, elliptical orbit at the outer edge of our solar system.

According to a report in National Geographic News, astronomers in Japan have said that they know where to find the Earth-sized planet.

"We have been able to identify more than 1,100 objects beyond Neptune since 1992, and a huge number of objects are showing large orbital eccentricities and elliptical orbits," said Tadashi Mukai, a professor at Kobe University's department of earth and planetary sciences.

This suggests that a body with sizeable mass must be influencing the movement of these objects by exerting a gravitational pull.

But the extreme distance and unusual orbit of the elusive "Planet X" have made it difficult to spot even with the most advanced telescopes.

Now, Mukai and colleagues propose that other researchers have simply been looking in the wrong place.

"We are now looking in places that we have not looked before, and I think we will be able to see the planet within the next five or ten years," said Mukai.

"We have reached our conclusions from simulations that explain the orbital elements," he added.

"Most surveys looking for Planet X are concentrated toward the ecliptic plane, since that is where most solar system objects concentrate," said Mark Sykes, director of the Planetary Science Institute in Tucson, Arizona.

The new models, however, suggest that Planet X is circling the sun on a 20 to 40 degree angle relative to the ecliptic plane.

In addition to its odd orbit, Planet X should have a diameter between 6,200 and 9,900 miles (10,000 and 16,000 kilometers), according to Mukai's team.

Despite its size, the planet will probably have a far lower density than Earth, the researchers think.

Earth has iron at its core, but if Planet X formed in the outer reaches of the solar system, it will have stone at its center and a mantle of ice.

The surface of the planet will probably be similar to that of Pluto-covered with ice made of water, ammonia, or methane with a surface temperature between -423.7 and -405.7 degrees Fahrenheit (-253.1 and -243.1 degrees Celsius).

Alternatively, if it is a "rogue" planet that took shape in the inner reaches of the solar system, the body could be mostly rock with a metallic core and its primordial atmosphere frozen on its surface.

Like Pluto, the new body would not dominate its orbit and so would not be classified as a planet under the recently changed definition of the International Astronomical Union.

ANI