Puny Pluto gets the boot as astronomers approve a new definition
PRAGUE (AP): Pluto, beloved by some as a cosmic underdog but scorned by astronomers who considered it too dinky and distant, has been unceremoniously stripped of its status as aplanet.
The International Astronomical Union, dramatically reversing course Thursday just a week after floating the idea of reaffirming Pluto's planethood and adding three new planets toEarth's neighborhood, downgraded the ninth rock from the sun in historic new galactic guidelines.
Powerful new telescopes, experts said, are changing the way they size up the mysteries of the solar system and beyond. But the scientists showed a soft side, waving plush toys of the Walt Disney character -- and insisting that Pluto's spirit will live on in the exciting discoveries yet to come.
"The word 'planet' and the idea of planets can be emotional because they're something we learn as children," said RichardBinzel, a professor of planetary science at the Massachusetts Institute of Technology, who helped hammer out the new definition.
"This is really all about science, which is all about getting new facts," he said. "Science has marched on ... Many more Plutos wait to be discovered."
Pluto, a planet since 1930, got the boot because it didn't meet the new rules, which say a planet not only must orbit the sun and be large enough to assume a nearly round shape, but must "clear the neighborhood around its orbit." That disqualifies Pluto, whose oblong orbit overlaps Neptune's, downsizing the solar system to eight planets from the traditional nine.
Astronomers have labored without a universal definition of a planet since well before the time of Copernicus, who proved tha tthe Earth revolves around the sun, and the experts gathered in Prague burst into applause when the guidelines were passed.
Predictably, Pluto's demotion provoked plenty of wistful nostalgia.
"It's disappointing in a way, and confusing," said PatriciaTombaugh, the 93-year-old widow of Pluto discoverer ClydeTombaugh.
"I don't know just how you handle it. It kind of sounds like Ijust lost my job," she said from Las Cruces, New Mexico. "But I understand science is not something that just sits there. It goes on. Clyde finally said before he died, 'It's there. Whatever it is. It is there."'
The decision by the IAU, the official arbiter of heavenly objects, restricts membership in the elite cosmic club to the eight classical planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
Pluto and objects like it will be known as "dwarf planets", which raised some thorny questions about semantics: If a raincoatis still a coat, and a cell phone is still a phone, why isn't a dwarf planet still a planet?
NASA said Pluto's downgrade would not affect its US$700million New Horizons spacecraft mission, which earlier this yearbegan a 9 1/2-year journey to the oddball object to unearth more of its secrets.
But mission head Alan Stern said he was "embarrassed" by Pluto's undoing and predicted that Thursday's vote would not end the debate. Although 2,500 astronomers from 75 nations attended the conference, only about 300 showed up to vote.
"It's a sloppy definition. It's bad science," he said. "It ain't over."
The shift also poses a challenge to the world's teachers, who will have to scramble to alter lesson plans just as schools open for the fall term.
"We will adapt our teaching to explain the new categories," said Neil Crumpton, who teaches science at a high school north of London. "It will all take some explanation, but it is really just
a reclassification and I can't see that it will cause any problems. Science is an evolving subject and always will be."
Under the new rules, two of the three objects that came tantalizingly close to planethood will join Pluto as dwarfs: the asteroid Ceres, which was a planet in the 1800s before it got demoted, and 2003 UB313, an icy object slightly larger than Pluto whose discoverer, Michael Brown of the California Institute of Technology, has nicknamed "Xena." The third object, Pluto's largest moon, Charon, isn't in line for any special designation.
Text of the resolutions approved Thursday by the IAU which define planets and downgrade Pluto:
The International Astronomical Union, dramatically reversing course Thursday just a week after floating the idea of reaffirming Pluto's planethood and adding three new planets toEarth's neighborhood, downgraded the ninth rock from the sun in historic new galactic guidelines.
Powerful new telescopes, experts said, are changing the way they size up the mysteries of the solar system and beyond. But the scientists showed a soft side, waving plush toys of the Walt Disney character -- and insisting that Pluto's spirit will live on in the exciting discoveries yet to come.
"The word 'planet' and the idea of planets can be emotional because they're something we learn as children," said RichardBinzel, a professor of planetary science at the Massachusetts Institute of Technology, who helped hammer out the new definition.
"This is really all about science, which is all about getting new facts," he said. "Science has marched on ... Many more Plutos wait to be discovered."
Pluto, a planet since 1930, got the boot because it didn't meet the new rules, which say a planet not only must orbit the sun and be large enough to assume a nearly round shape, but must "clear the neighborhood around its orbit." That disqualifies Pluto, whose oblong orbit overlaps Neptune's, downsizing the solar system to eight planets from the traditional nine.
Astronomers have labored without a universal definition of a planet since well before the time of Copernicus, who proved tha tthe Earth revolves around the sun, and the experts gathered in Prague burst into applause when the guidelines were passed.
Predictably, Pluto's demotion provoked plenty of wistful nostalgia.
"It's disappointing in a way, and confusing," said PatriciaTombaugh, the 93-year-old widow of Pluto discoverer ClydeTombaugh.
"I don't know just how you handle it. It kind of sounds like Ijust lost my job," she said from Las Cruces, New Mexico. "But I understand science is not something that just sits there. It goes on. Clyde finally said before he died, 'It's there. Whatever it is. It is there."'
The decision by the IAU, the official arbiter of heavenly objects, restricts membership in the elite cosmic club to the eight classical planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
Pluto and objects like it will be known as "dwarf planets", which raised some thorny questions about semantics: If a raincoatis still a coat, and a cell phone is still a phone, why isn't a dwarf planet still a planet?
NASA said Pluto's downgrade would not affect its US$700million New Horizons spacecraft mission, which earlier this yearbegan a 9 1/2-year journey to the oddball object to unearth more of its secrets.
But mission head Alan Stern said he was "embarrassed" by Pluto's undoing and predicted that Thursday's vote would not end the debate. Although 2,500 astronomers from 75 nations attended the conference, only about 300 showed up to vote.
"It's a sloppy definition. It's bad science," he said. "It ain't over."
The shift also poses a challenge to the world's teachers, who will have to scramble to alter lesson plans just as schools open for the fall term.
"We will adapt our teaching to explain the new categories," said Neil Crumpton, who teaches science at a high school north of London. "It will all take some explanation, but it is really just
a reclassification and I can't see that it will cause any problems. Science is an evolving subject and always will be."
Under the new rules, two of the three objects that came tantalizingly close to planethood will join Pluto as dwarfs: the asteroid Ceres, which was a planet in the 1800s before it got demoted, and 2003 UB313, an icy object slightly larger than Pluto whose discoverer, Michael Brown of the California Institute of Technology, has nicknamed "Xena." The third object, Pluto's largest moon, Charon, isn't in line for any special designation.
Text of the resolutions approved Thursday by the IAU which define planets and downgrade Pluto:
Contemporary observations are changing our understanding of planetary systems, and it is important that our nomenclature for objects reflect our current understanding. This applies, in particular, to the designation "planets." The word "planet" originally described "wanderers" that were known only as moving lights in the sky. Recent discoveries lead us to create a new definition, which we can make using currently available scientific information.
The IAU therefore resolves that "planets" and other bodies, except satellites, in our Solar System be defined into three distinct categories in the following way:
(1) A "planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.
(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a
hydrostatic equilibrium (nearly round) shape, (c) has not cleared theneighbourhood around its orbit, and (d) is not a satellite.
(3) All other objects, except satellites, orbiting the Sun shall be referred to
collectively as "Small Solar-System Bodies."
The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
The IAU further resolves: Pluto is a "dwarf planet" by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects.
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