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Pluto has lost its status as the ninth planet of the solar system. [File photo]

Pluto has lost its status as the ninth planet of the solar system. [File photo] (ABC TV)

Mixed reaction to Pluto's demotion

There have been mixed reactions to the decision to strip Pluto of its status as a planet, after astronomers from around the world redefined it as a "dwarf planet", leaving just eight major planets in the solar system.

A heated debate among 2,500 scientists from the International Astronomical Union (IAU) meeting in Prague, drew a clear distinction between Pluto and the other eight planets.

With the vote, toys and models of the solar system became instantly obsolete, forcing teachers and publishers to scramble to update textbooks and lessons used in classrooms for decades.

Traditional planets will be restricted to eight: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

"Pluto is dead," Mike Brown of the California Institute of Technology said.

The need to define what is a planet was driven by technological advances enabling astronomers to look further into space and measure more precisely the size of celestial bodies.

University of Chicago spokesman Richard H Miller says it is an issue mainly for the public, not really for scientists.

"Some people may be upset, but we've long regarded it (Pluto) as a minor planet," he said.

But the overseer of science investigations on NASA's New Horizons mission to Pluto, Alan Stern of the South-west Research Institute in Boulder in Colorado, calls the reclassification rash and illogical.

"I think people are going to consider Pluto a planet regardless," he said.

Officials at the American Museum of Natural History in New York had been at the vanguard of the movement to demote Pluto and are feeling vindicated.

"We had enormous numbers of telephone calls and I would say things that verged on hate mail from second-graders - very angry children who said, 'What have you done? This is the cutest, most Disney-esque of the planets. How could you possibly demote it?'" Michael Shara, the museum's astrophysics curator, said.

While the museum staff are celebrating, he says Pluto's new status is more a victory for the astronomical community because it now has a "greatly increased understanding of what a planet is".

The agreed-upon definition - the first time the IAU has tried to define scientifically what a planet is - comes in sharp contrast to the draft sent around to delegates at the General Assembly last week.

That document, which kept Pluto as a planet and would have added three others, touched off a revolt that grew daily.

Some delegates appeared downright hostile to the notion.

Founder's widow

Discovered in 1930 by the American Clyde Tombaugh, the icy rock of Pluto has traditionally been considered the ninth planet, farthest from the sun in the solar system.

Tombaugh's widow Patricia says the discoverer, like any good scientist, would have accepted the demotion as inevitable.

"Clyde would have said, 'Science is a progressive thing and if you're going to be a scientist and put your neck out, you're apt to have it bitten upon'," the 94-year-old said from her home in New Mexico.

She adds a small amount of her husband's ashes are now on a spacecraft bound for Pluto.

Richard Binzel, professor of Planetary Sciences at The Massachusetts Institute of Technology (MIT) and a member of the planet definition committee, says the decision is all about the advancement of science changing thinking as more information is obtained.

"The significance is that new discoveries and new science have told us that there is something different about Pluto from the other eight planets and as science learns more information, we get new results and new considerations," he said.

Xena definition

He addsimpetus to the decades-old debate on the definition of a planet when he discovered UB313 in 2003.

Xena, as it is nicknamed, is larger than Pluto, instantly creating a buzz over whether a new planet had been discovered.

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 be large enough in 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 oblong orbit overlaps Neptune's.

Xena also does not make the grade of being a planet, and will also be known as a dwarf planet.

Astrological impact

Meanwhile, astrologers foretell no major changes in the way they read the heavens because of the decision to downgrade pluto.

British astrologer Russell Grant says Pluto's planetary demotion is not a surprise after years of discussion and he will not change the charts he uses for his clients.

"I personally am shaken, not stirred," he said.

"It's very interesting that Pluto's been downgraded in a planetary sense because he could never be downgraded in a mythological sense."

He also says astrologers have long used non-planets, such as Earth's moon.

He also charts several asteroids, which are inside the solar system but much smaller than planets.

"I will continue to use Pluto because he gives me the ability to look into people's charts and see where they're coming from psychologically," he said.

- Reuters

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A meeting of international astronomers has reclassified Pluto as a dwarf planet.

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Pluto is officially no longer a planet - the International Astronomical Union has officially downgraded its status to dwarf planet, and the solar system now consists of eight planets rather than nine.

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