The planethood of Pluto put to rest
Michelle Bauman
Issue date: 11/11/08 Section: News
The University of Dallas Physics Department held a public observatory viewing on Wednesday evening, accompanied by a brief lecture on the criteria for planethood.
Dr. Richard Olenick of the physics department presented the lecture on what constitutes a planet. "In 2006, Pluto lost its standing as a planet, leaving our solar system with only eight planets," he said. He went on to examine what defines a planet and why Pluto fails to meet these standards, looking at the criteria of size, shape, orbit, temperature and composition.
"Although popular affection and sentimentality for Pluto remain, advances in our viewing technology into space have brought scientists to the conclusion that it just isn't a planet," said Olenick, who then cited significant differences between Pluto and the other planets. "The other eight planets all orbit on the same plane, but Pluto's orbit is on a different plane, inclined from the rest," Olenick explained.
Olenick described the composition of the solar system, explaining that in addition to the sun and planets, the solar system contains the asteroid belt, which includes over 1,000 asteroids, and the Oort Comet Cloud, which is believed to be the source of comets in random orbits around the solar system. "Another feature of the solar system is the Kuiper Belt," said Olenick. "The Kuiper Belt is located outside the orbit of Neptune, and it contains icy asteroids and other bodies, several of which are as big as or even bigger than Pluto." This discovery led scientists to question the definition of a planet. "Rather than classifying all of these other objects as planets as well, scientists decided to remove Pluto's status as a planet, determining it instead to be a Kuiper Belt Object," he said.
"The International Astronomical Union (IAU) has been working on establishing criteria to define which objects in space qualify as planets," said Olenick. To be a planet, the IAU concluded, an object must orbit a star without being a star itself, be massive enough that its own gravity makes it round, and dominate its orbital. While Pluto meets these first two conditions, it does not dominate its orbital region and thus is not classified as a real planet, but as a dwarf planet.
After the lecture, Olenick took students to the observatory, where they were able to view Jupiter and several of its moons, as well as other objects in space.
Dr. Richard Olenick of the physics department presented the lecture on what constitutes a planet. "In 2006, Pluto lost its standing as a planet, leaving our solar system with only eight planets," he said. He went on to examine what defines a planet and why Pluto fails to meet these standards, looking at the criteria of size, shape, orbit, temperature and composition.
"Although popular affection and sentimentality for Pluto remain, advances in our viewing technology into space have brought scientists to the conclusion that it just isn't a planet," said Olenick, who then cited significant differences between Pluto and the other planets. "The other eight planets all orbit on the same plane, but Pluto's orbit is on a different plane, inclined from the rest," Olenick explained.
Olenick described the composition of the solar system, explaining that in addition to the sun and planets, the solar system contains the asteroid belt, which includes over 1,000 asteroids, and the Oort Comet Cloud, which is believed to be the source of comets in random orbits around the solar system. "Another feature of the solar system is the Kuiper Belt," said Olenick. "The Kuiper Belt is located outside the orbit of Neptune, and it contains icy asteroids and other bodies, several of which are as big as or even bigger than Pluto." This discovery led scientists to question the definition of a planet. "Rather than classifying all of these other objects as planets as well, scientists decided to remove Pluto's status as a planet, determining it instead to be a Kuiper Belt Object," he said.
"The International Astronomical Union (IAU) has been working on establishing criteria to define which objects in space qualify as planets," said Olenick. To be a planet, the IAU concluded, an object must orbit a star without being a star itself, be massive enough that its own gravity makes it round, and dominate its orbital. While Pluto meets these first two conditions, it does not dominate its orbital region and thus is not classified as a real planet, but as a dwarf planet.
After the lecture, Olenick took students to the observatory, where they were able to view Jupiter and several of its moons, as well as other objects in space.
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