29 February 2008

Earth-sized planet predicted beyond Pluto

Agence France-Presse
Japanese scientists believe another planet, up to two-thirds the size of Earth, is orbiting in the far reaches of the Solar System.
Earth-sized planet predicted beyond Pluto

Waiting in the wings: An artist's illustration showing a planet two-thirds the size of the Earth, which is believed by Japanese researchers to be in the outer reaches of the Solar System.

TOKYO: Japanese scientists believe another planet, up to two-thirds the size of Earth, is orbiting in the far reaches of the Solar System.

The researchers at Kobe University in western Japan said calculations using computer simulations led them to conclude it was only a matter of time before the mysterious, new “Planet X” was found.

Much bigger than Pluto

“Because of the very cold temperature, its surface would be covered with ice, icy ammonia and methane,” said lead researcher Tadashi Mukai. The study by Mukai and co-worker Patryk Lykawka will be published in the April issue of the Astronomical Journal.

“The possibility is high that a yet unknown, planet-class celestial body, measuring 30 per cent to 70 per cent of the Earth’s mass, exists in the outer edges of the Solar System,” says a statement released by the University.

“If research is conducted on a wide scale, the planet is likely to be discovered in less than 10 years,” it claims.

This Planet X – so called by scientists as it is yet unfound – would have an oblong elliptical solar orbit and circle the sun every thousand years, the team said, estimating its radius was 15 to 26 billion km.

Pluto de-listed

The study comes two years after school textbooks had to be rewritten when Pluto was booted out of the list of planets.

Pluto was discovered by the American astronomer Clyde Tombaugh in 1930 in the so-called Kuiper belt, a chain of icy debris in the outer reaches of the solar system. In 2006, nearly a decade after Tombaugh’s death, the International Astronomical Union ruled the celestial body was merely a ‘dwarf planet’ in the cluttered Kuiper belt.

The astronomers said Pluto’s oblong orbit overlapped with that of Neptune, excluding it from being a planet. It defined the Solar System as consisting solely of the classical set of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

The team noted that more than 1,100 celestial bodies have been found in the outer reaches of the Solar System since the mid-1990s. “But it would be the first time to discover a celestial body of this size, which is much larger than Pluto,” Mukai said.

Celestial movements

The researchers set up a theoretical model looking at how the remote area of the Solar System would have evolved over the past four billion years.

“In coming up with an explanation for the celestial bodies, we thought it would be most natural to assume the existence of a yet unknown planet,” Mukai said. “Based on our hypothesis, we calculated how debris moved over the past four billion years. The result matched the actual movement of the celestial bodies we can observe now.”

He was hopeful about research by Kobe University, the University of Hawaii and Taiwan’s National Central University. “We are expecting that the ongoing joint celestial observation project will eventually discover Planet X,” Mukai said.


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