Planetary detective is sure the truth is out there

A BRITISH scientist believes he has found convincing evidence for the existence of an undiscovered planet orbiting the Sun in the outermost reaches of the solar system.

A BRITISH scientist believes he has found convincing evidence for the existence of an undiscovered planet orbiting the Sun in the outermost reaches of the solar system.

The planet - if it is shown to exist - would be larger than Jupiter, the biggest of the other nine planets, and is likely to have once wandered through interstellar space before being captured by the gravitational pull of the Sun.

Despite its enormous size, astronomers have failed to observe the planet because it reflects hardly any light and moves so slowly in the sky, said Dr John Murray, a planetary scientist at the Open University in Milton Keynes.

However, the planet's own gravity is strong enough to affect the orbits of comets in the solar system, which has enabled Dr Murray to calculate the planet's position, roughly 33,000 times further away from the Sun than the Earth.

Existing theories about the origin of comets predict that their orbits should be random affairs but Dr Murray found that at least 13 of them are strictly aligned, suggesting that the gravitational effects of a hitherto unknown object is marshalling their movements.

Dr Murray calculated the chances of the non-random orbits of the 13 comets occurring by chance alone are about 1,700-to- one. "Whatever happens, there is something here to be explained. At the moment I can't find a more likely explanation of this finding than there being another planet," Dr Murray said. The planet would have to be at least as massive as Jupiter to provide sufficient gravitational kick to alter the orbital paths of the comets around the Sun.

It could even be as large as a "brown dwarf" star - the coolest type of a star - which can be more than ten times as massive as Jupiter.

Dr Murray favours the idea of it being a large planet-sized object that escaped from its own star and wandered into the path of our own Sun at some point in the distant past. "I think there's no doubt that it's not an original member of the solar system but has been captured from elsewhere," he said.

The research into the "tenth planet" is due to be published next week in the Monthly Notices of the Royal Astronomical Society. It will coincide with a study being presented at an astronomy conference in Italy on Monday, when an American team led by Professor John Matese of the University of Louisiana at Lafayette will come to a similar conclusion.

"I was looking at the origin of comets three years ago and it first occurred to me then that they were associated with an unknown planet, but it seemed a ridiculous idea," Dr Murray said. "It is good to think someone else has reached a similar conclusion." By plotting the position of comets at their farthest points from the Sun - the aphelion - Dr Murray found that a significant number could be aligned in a straight line, indicating the external influence of a large object. He has worked out that the planet, if it exists, currently lies somewhere in the direction of the constellation Delphinus, the Dolphin.

Two scientific journals rejected Dr Murray's paper before it was accepted by the Royal Astronomical Society. "I can understand the scepticism because it would be a surprising result if it turns out to be true," he said.

Astronomers have long suspected there might be a "tenth planet" orbiting the sun beyond Pluto, but this was based on perturbations to the orbit of Neptune, which would not be affected by the object discovered by Dr Murray. Big discovery and the nine heavenly bodies it may be about to eclipse

Mercury

Diameter: 3,031 miles.36 million miles from the Sun. Not much bigger than the Moon, what little atmosphere Mercury has is helium.

Venus

Diameter: 7,520 miles. 67.2 million miles from the Sun. Like Earth but hotter (465C) thanks to a runaway greenhouse effect.

Earth

Diameter: 8,000 miles. 93 million miles from the Sun. The only place were life is known to exist. The "pale blue dot" of the solar system.

Mars

Diameter: 4,217 miles. 141 million miles from the Sun. The red planet, named after the Roman war god. May once have hosted life.

Jupiter

Diameter: 88,846 miles. 483.6 million miles from the Sun. A globe of liquid and gas, it is heavier than all other planets combined.

Saturn

Diameter: 67,570 miles. 887 million miles from the Sun. Second in size to Jupiter, Saturn is famous for its icy rings.

Uranus

Diameter: 31,035 miles. 1,784m miles from the Sun. Seen as planet in 1781; named after Saturn's mythological father.

Neptune

Diameter: 30,775 miles. 2,794 million miles from the Sun. Discovered in 1846, has winds gusting to 1,240 mph.

Pluto

Diameter: 1,419 miles. 4,583 million miles from the Sun. Discovered in 1930, Pluto is farthest planet from the Sun yet found.

Planet X

Diameter: unknown. 3,300 billion miles from the Sun. If it exists, Planet X could be 10 times more massive than Jupiter.