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Topic: Pluto planet

	Pluto
		Pluto is smaller than seven of the solar system's moons (the Moon, Io, Europa, Ganymede, Callisto, Titan and Triton).
		The planet received this name (after many other suggestions) perhaps because it's so far from the Sun that it is in perpetual darkness and perhaps because "PL" are the initials of Percival Lowell.
		Pluto's atmosphere may exist as a gas only when Pluto is near its perihelion; for the majority of Pluto's long year, the atmospheric gases are frozen into ice.
	www.nineplanets.org /pluto.html (1526 words)

	SPACE.com -- Pluto Demoted: No Longer a Planet in Highly Controversial Definition
		Pluto and its moon Charon, which would both have been planets under the initial definition proposed Aug. 16, now get demoted because they are part of a sea of other objects that occupy the same region of space.
		The initial proposal, hammered out by a group of seven astronomers, historians and authors, attempted to preserve Pluto as a planet but was widely criticized for diluting the meaning of the word.
		Pluto, discovered in 1930, was at first thought to be larger than it is. It has an eccentric orbit that crosses the path of Neptune and also takes it well above and below the main plane of the solar system.
	www.space.com /scienceastronomy/060824_planet_definition.html (1034 words)

	Pluto
		Pluto is smaller than seven of the solar system's moons (the Moon, Io, Europa, Ganymede, Callisto, Titan and Triton).
		The planet received this name (after many other suggestions) perhaps because it's so far from the Sun that it is in perpetual darkness and perhaps because "PL" are the initials of Percival Lowell.
		Pluto's atmosphere may exist as a gas only when Pluto is near its perihelion; for the majority of Pluto's long year, the atmospheric gases are frozen into ice.
	seds.lpl.arizona.edu /nineplanets/nineplanets/pluto.html (1526 words)

	Pluto - MSN Encarta
		Pluto’s orbit is so eccentric that at certain points along its path Pluto is slightly closer to the Sun than is Neptune.
		Pluto was discovered as the result of a telescopic search inaugurated in 1905 by American astronomer Percival Lowell, who postulated the existence of a distant planet beyond Neptune as the cause of slight irregularities in the orbits of Uranus and Neptune.
		Pluto survived the collision, according to this theory, and the material that afterward was thrown into orbit around Pluto eventually formed Charon and the two newly discovered moons.
	encarta.msn.com /encyclopedia_761562181/Pluto_(planet).html (1656 words)

	Pluto - Wikipedia, the free encyclopedia
		The planet Pluto was originally discovered in 1930 in the course of a search for a body sufficiently massive to account for supposed anomalies in the orbits of Uranus and Neptune.
		Pluto's discovery was mostly due to the thoroughness and diligence of Tombaugh's search, which he continued for some time after the discovery and left him satisfied that no other planet of a comparable magnitude existed.
		While Pluto's identification as Planet X began to be doubted soon after its discovery, and for some decades afterwards some considered that a hypothetical tenth planet might be the true Planet X which supposedly caused anomalies in Uranus and Neptune's position, Pluto's identity as the solar system's ninth planet was unquestioned until the 1990s.
	en.wikipedia.org /wiki/Pluto_(planet) (3573 words)

	Pluto (planet) - Encyclopedia.WorldSearch (Site not responding. Last check: 2007-11-07)
		Pluto was discovered by the astronomer Clyde W. Tombaugh at the Lowell Observatory in Arizona on February 18, 1930 when he compared photographic plates taken on January 23 and 29.
		Pluto was determined to have an atmosphere from an occultation observation in 1988.
		Planet X? The planet Pluto was originally discovered in 1930 in the course of a search for a body sufficiently massive to account for supposed anomalies in the orbits of Uranus and Neptune.
	encyclopedia.worldsearch.com /pluto_(planet).htm (2534 words)

	Is Pluto A Planet? (Site not responding. Last check: 2007-11-07)
		This definition distinguishes planets from asteroids and comets, which directly orbit our star, but are generally not large enough to be pulled into a spherical shape by their own gravity, and it distinguishes planets from stars, which frequently are in direct orbit around other stars, but generate heat internally by nuclear fusion.
		Pluto is unlike the other planets in that it has an icy surface instead of a rocky surface like the inner 4 (terrestrial) planets, or a deep atmosphere like the next 4 (gas giant) planets.
		Pluto was discovered serendipitously by Lowell Observatory astronomers searching for what was then known as 'Planet X', yet Pluto is far to small to be Planet X. Its planethood was, and still is primarily due to a PR campaign launched by the Observatory at the time of discovery (1930), rather than Pluto's properties.
	mips.as.arizona.edu /~stansber/Planet.html (2207 words)

	ASTRONOMY (PLUTO. a dwarf planet) (Site not responding. Last check: 2007-11-07)
		Henceforth Pluto is deemed a "dwarf planet." Tiny, mysterious Pluto is so far from the Sun that it appears only as a tiny speck of light that moves slowly against the background of the fixed stars.
		Pluto was considered the most distant of the planets, yet the eccentricity of its orbit periodically carries it inside Neptune's orbit, where it has been since 1979 and where it remained until March 1999.
		Ground-based observations indicate that Pluto's surface is covered with methane ice and that there is a thin atmosphere that may freeze and fall to the surface as the planet moves away from the Sun.
	www.jsc.nasa.gov /er/seh/pluto.html (1124 words)

	Pluto
		Pluto is usually farther from the Sun than any of the nine planets; however, due to the eccentricity of its orbit, it is closer than Neptune for 20 years out of its 249 year orbit.
		Pluto's temperature varies widely during the course of its orbit since Pluto can be as close to the sun as 30 AU and as far away as 50 AU.
		Pluto was officially labeled the ninth planet by the International Astronomical Union in 1930 and named for the Roman god of the underworld.
	www.solarviews.com /eng/pluto.htm (1746 words)

	ipedia.com: Pluto (planet) Article (Site not responding. Last check: 2007-11-07)
		Pluto is not only much smaller and less massive than every other planet, it is also smaller and less massive than seven moonss of other planets: Ganymede, Titan, Callisto, Io, Earth's Moon, Europa and Triton.
		Pluto has an atmosphere when it is close to perihelion; the atmosphere may freeze out as Pluto moves further from the Sun.
		Originally, it was believed that Pluto was larger than Mercury but smaller than Mars, but that calculation was based on the premise that a single object was being observed; once it was realized that there were in fact two objects instead of one, the estimated size of Pluto was revised downward.
	www.ipedia.com /pluto__planet_.html (2288 words)

	Pluto
		At the time, it didn't matter that this planet was in the "wrong" place to account for the perturbations, and it was later determined that the differences in Neptune's orbit could be accounted for by other things.
		It was discovered at a time when people were looking for another planet in that region of space, and when they were not looking for a large belt of cometary objects, as we are now (see the discussion of the Kuiper Belt).
		Pluto is named after the ancient Roman god of the underworld, which is a fitting name for a planet that lies so far from the warm Sun, receiving only 1/16,000 of the light we receive on Earth.
	filer.case.edu /~sjr16/planets_dwarf_pluto.html (1116 words)

	The Planet Pluto
		Pluto is usually the furthest planet from our Sun in the solar system, residing at an average distance of 3.6 billion miles.
		The surface of Pluto is frozen methane, possibly formed from methane which fell from the atmosphere.
		Some astronomers argue, that instead of "demoting" Pluto from a planet to a minor planet, that Ceres should be "promoted" to a planet.
	www.crh.noaa.gov /fsd/astro/pluto.php (919 words)

	PLUTO - ENCHANTED LEARNING SOFTWARE
		Pluto is 39 times farther from than the sun than the Earth is. Pluto ranges from 2.8 to 4.6 billion miles (4.447 billion to 7.38 billion km) from the Sun.
		Pluto has a very eccentric orbit; that means that its distance from the sun varies a lot during its orbit around the sun.
		Pluto's orbit is tilted from the plane of the ecliptic.
	www.enchantedlearning.com /subjects/astronomy/planets/pluto (1048 words)

	A New Solar System - Explore the Cosmos \| The Planetary Society
		Pluto and its neighbors, argued critics of the committee's proposal, are too small to be considered planets.
		The true planets, argue proponents of the eight-planet solar system, are naturally distinguishable from the plethora of large and small objects at the edge of the solar system, and our definition of "planet" should reflect that.
		Similar to the Planet Definition Committee's proposal, the resolution states that "a planet is a celestial body that (a) is in orbit around the Sun and (b) has sufficient mass for its self-gravity to overcome rigid-body forces so that it assumes a hydrostatic equilibrium (nearly round) shape.
	www.planetary.org /explore/topics/pluto/new_solarsystem.html (2772 words)

	National Geographic News @ nationalgeographic.com (Site not responding. Last check: 2007-11-07)
		The scientists' main reason for the switch is Pluto's tiny size; with a diameter of approximately 1,420 miles (2,280 kilometers) it is six times smaller than Earth, and smaller than seven of the solar system's moons.
		Despite its unusual characteristics, Pluto's status as a planet was solid until 1992, when David Jewitt and J. Luu of the University of Hawaii discovered a strange object called 1992 QB1.
		Pluto is the only planet in the solar system that has not been visited by a space probe.
	news.nationalgeographic.com /news/2001/02/0216_Pluto.html (639 words)

	A Short History of Pluto, the un-Planet
		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 neighborhood around its orbit.
		Translation: To be a planet, a world must have enough mass and gravity to gather itself into a ball; it must orbit the sun; and it must reign supreme in its own orbit, having "cleared the neighborhood" of other competing bodies.
		The neighborhood is a mess and, thus, Pluto is not a planet.
	www.plutopetition.com /unplanet.php (1220 words)

	NASA's Solar System Exploration: Planets: Pluto: Overview
		According to the new rules a planet meets three criteria: it must orbit the Sun, it must be big enough for gravity to squash it into a round ball, and it must have cleared other things out of the way in its orbital neighborhood.
		(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 neighborhood 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 the neighborhood around its orbit, and (d) is not a satellite.
	solarsystem.jpl.nasa.gov /planets/profile.cfm?Object=Pluto&Display=Overview (386 words)

	Much ado about Pluto
		Pluto is the only planet that has not been visited by a spacecraft.
		Pluto's composition is unknown, but its density (about 2 gm/cm3) indicates that it is probably a mixture of rock and ice.
		It seems that Pluto is a sentimental favorite to remain a planet among both scientists and the public.
	science.nasa.gov /newhome/headlines/ast17feb99_1.htm (1376 words)

	Planet Pluto - Pluto-Kuiper Express
		Pluto is the farthest known planet from the Sun.
		Pluto's orbit from the Sun varies from 4.4 to 7.7 billion kms and for the most of its orbit it is the outer most planet.
		Between 1979 and 1999 Pluto was actually closer to the Sun than Neptune and the closest approach to the sun (perihelion) was in September 1989.
	www.aerospaceguide.net /planet/planetpluto.html (438 words)

	New Planet
		While Pluto's surface is moderately red, the new dwarf planet appears almost white, and while Pluto has a mottled-looking surface which reflects on average 60% of the sunlight which hits it, the new planet appears essentially uniform and reflects 86% (+/- 7%) of the light that hits it.
		Pluto, we know, has a density about midway between ice and rock, thus we think that it is made of about half and half ice and rock on the inside.
		Culturally, however, the idea that Pluto is a planet is enshrined in a million different ways, from plastic placemats depicting the solar system that include the nine planets, to official NASA web sites, to mnemonics that all school children learn to keep the nine planets straight, to U.S. postage stamps.
	www.gps.caltech.edu /~mbrown/planetlila (5922 words)

	Pluto Information 1 (Site not responding. Last check: 2007-11-07)
		Pluto's orbit has an eccentricity of 0.25, which means that Pluto's distance to the sun is as little as 29.7 AU (temporarily making it closer than Neptune) and as great as 49.7 AU.
		Pluto's rotation rate (6.4 days) was measured in 1954, but the breakthrough observation that first gave an idea of conditions on Pluto was the discovery of methane in 1976.
		It also implied that Pluto was a bright, frost-covered planet, which in turn implied that Pluto was a small planet with a bright surface as opposed to a large planet with a darker surface.
	dosxx.colorado.edu /Pluto/pluto1.html (551 words)

	APOD Index - Solar System: Pluto
		Pluto is still considered to be a planet, although very little is known about it compared to other planets.
		Pluto is smaller than any other planet and even smaller than several other planet's moons.
		Pluto and Charon are bright enough to create diffraction spikes in this Hubble Space Telescope image, but Nix and Hydra are some 5,000 times fainter than Pluto and appear only as small points of light.
	antwrp.gsfc.nasa.gov /apod/pluto.html (430 words)

	BBC NEWS \| Science/Nature \| Pluto loses status as a planet
		Pluto, which was discovered in 1930 by the American Clyde Tombaugh, will be referred to as a "dwarf planet".
		Pluto was automatically disqualified because its highly elliptical orbit overlaps with that of Neptune.
		Named after the god of the underworld in Roman mythology, Pluto orbits the Sun at an average distance of 5.9 billion kilometres (3.7 billion miles) taking 247.9 Earth years to complete a single circuit of the Sun.
	news.bbc.co.uk /2/hi/science/nature/5282440.stm (608 words)

	Pluto, planet and Greek god of wealth.
		The search for this planet was inspired by the fact that the discovery of the eighth planet, Neptune, did not completely account for the irregularities in the orbit of the seventh planet, Uranus.
		Since the ninth planet moves farthest from the light of the sun and farther into the darkness of the space between the stars, it was named Pluto (whose name happens to begin with the initials of Percival Lowell), after the Roman god of the underworld, lord of the dead, and giver of wealth.
		Pluto’s rocky core is covered with a thick layer of water ice, overlaid with a layer of ice mixed with frozen methane.
	www.wordsources.info /pluto.html (806 words)

	Astronomy For Kids - Pluto - KidsAstronomy.com
		Pluto was thought to be the god to whom all men must eventually go.
		Pluto is smaller than 7 of the moons in the Solar System.
		Pluto is so far away, that no satellites have ever been sent there.
	www.kidsastronomy.com /pluto.htm (254 words)

	Welcome to the Pluto Home Page (Site not responding. Last check: 2007-11-07)
		The Pluto symbol is made from the initials of Percival Lowell, the astronomer who searched for a ninth planet for many years and after whom the Lowell Observatory (where Clyde Tombaugh discovered Pluto) is named.
		Radius of Pluto = 1145 to 1200 km
		PLUTO: Discovered in 1930 by American astronomer Clyde W. Tombaugh at Lowell Observatory in Flagstaff, AZ during a systematic search for a trans-Neptune planet predicted by Percival Lowell and William H. Pickering.
	dosxx.colorado.edu /plutohome.html (943 words)

	The Planets: Understanding Astrology - astrology.com
		Pluto's energy may be subtle, but its results will hit you like a ton of bricks.
		Pluto says 'out with the old and in with the new,' and we'd better be ready for it.
		Pluto is the last of the transcendental Planets and is the higher octave of Mars.
	www.astrology.com /aboutastrology/interpreting/planets/pluto.html (284 words)

	Scientists: Pluto not a planet - Space.com - MSNBC.com
		Pluto and its moon Charon, which would both have been planets under the initial definition proposed Aug. 16, now get demoted because they are part of a sea of other objects that occupy the same region of space.
		Pluto, discovered in 1930, was at first thought to be larger than it is. It has an eccentric orbit that crosses the path of Neptune and also takes it well above and below the main plane of the solar system.
		Even though Pluto may have lost its official status as a planet, the frozen world and its kin are still worthy of study, says Louis Friedman, executive director of the nonprofit Planetary Society.
	www.msnbc.msn.com /id/14489259 (1328 words)

	StarChild: The Dwarf Planet Pluto
		Pluto has more in common with Triton, Neptune's largest moon, than it does with any of the eight planets in our solar system.
		Pluto is tilted 122.5 degrees on its axis, which basically means that it is rotating on its head!
		Pluto was re-classified as a dwarf planet in August 2006.
	starchild.gsfc.nasa.gov /docs/StarChild/solar_system_level2/pluto.html (306 words)

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