[QODLink]
Archive
Pluto kicked out of the planets
Pluto has lost its status as the ninth and outermost planet of the solar system, the world's leading astronomical body has decided.
Last Modified: 24 Aug 2006 15:08 GMT
Pluto will be put into a category called dwarf planets
Pluto has lost its status as the ninth and outermost planet of the solar system, the world's leading astronomical body has decided.

After a heated debate, 2,500 scientists and astronomers voted at the International Astronomical Union (IAU) on Thursday that Pluto, which has been called a planet since being discovered in 1930, would be put into a category called "dwarf planets".

The IAU resolution said: "The eight planets are Mercury, Earth, Venus, Mars, Jupiter, Saturn, Uranus and Neptune."

Pluto's status had been contested for many years by astronomers who said that its tiny size and highly eccentric orbit precluded it from joining the other acknowledged planets.

The need to define what it takes to be a planet stems from technological advances that enable astronomers to look farther into space and to measure more precisely the size of celestial bodies in our solar system.

The scientists agreed that to be called a planet, a celestial body must be in orbit around a star while not itself being a star.

It must also have sufficient mass for its own gravity to pull it into a nearly spherical shape and have cleared the neighbourhood around its orbit.

Pluto was disqualified because its orbit overlaps that of Neptune.

In addition to the categories of "planet" and "dwarf planet", the definition creates a third category to encompass all other objects, except satellites, to be known as small solar system bodies.

Discovery of Xena

The anti-Pluto movement gained ground after the discovery of a distant object beyond Pluto's orbit called 2003 UB313, also known unofficially as Xena.

Its discoverer said UB313 was as big as Pluto and thus could lay claim to being a planet.

Pluto was discovered on February 18, 1930, by an American astronomer, Clyde Tombaugh, then aged 24.

Named after the god of the underworld in classical mythology, it orbits the Sun at an average distance of 5,906,380,000 kilometres, taking 247.9 Earth years to complete a single circuit.

An unmanned US spacecraft, New Horizons, is due to fly by Pluto and the Kuiper Belt in 2015.

Source:
Agencies
Topics in this article
Organisation
Featured on Al Jazeera
An innovative rehabilitation programme offers Danish fighters in Syria an escape route and help without prosecution.
Street tension between radical Muslims and Holland's hard right rises, as Islamic State anxiety grows.
Take an immersive look at the challenges facing the war-torn country as US troops begin their withdrawal.
Ministers and MPs caught on camera sleeping through important speeches have sparked criticism that they are not working.
Featured
Referendum on Scottish independence is the first major election in the UK where 16 and 17-year olds get a vote.
Blogger critical of a lack of government transparency faces defamation lawsuit from Prime Minister Lee Hsien Loong.
Farmers worry about their future as buyers shun local produce and rivers show an elevated presence of heavy metals.
War-torn neighbour is an uncertain haven for refugees fleeing Pakistan's Balochistan, where locals seek independence.
NSA whistleblower Snowden and journalist Greenwald accuse Wellington of mass spying on New Zealanders.
join our mailing list