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標題: It's official--Pluto's out [打印本頁]

作者: jhl445 時間: 2006-8-25 03:37 AM 標題: It's official--Pluto's out

We All Know that Pluto is an planet when I was a kid in 25yrs ago, It is so sad that Pluto is removed from the solar system.
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The International Astronomical Union has voted to remove Pluto from the solar system--as a planet, that is.

Meeting in Prague over the past week, IAU members rejected a proposal to increase the number of planets to 12 by including Ceres, the largest known asteroid, which orbits between Mars and Jupiter; Charon, which has been considered Pluto's moon; and 2003 UB313, an object nicknamed "Xena" that was discovered in 2005 orbiting far beyond Pluto. ! w" H1 T. X6 r) B, P4 O+ e& m

Pluto is now considered a "dwarf planet" because it has an oblong orbit that overlaps with Neptune's orbit.

Ceres and Xena will also be considered dwarf planets. Charon is simply one of the "small solar system bodies." 5.39.217.76/ K0 i" X' Y7 o4 {; [3 z

Here are images from the Hubble Space Telescope in February that confirmed the existence of two new moons orbiting Pluto. Pluto and Charon are gravitationally locked so the same sides always face each other. They orbit each other every 6.3 Earth days.( c& J9 F. e" E$ ^* R O- i
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On Jan. 19, NASA launched the New Horizons spacecraft on a 3-billion-mile journey to reach Pluto and Charon in the summer of 2015. The piano-size craft, designed and built at Johns Hopkins University's Applied Physics Laboratory, will travel at a record 36,000mph after bouncing off Jupiter's gravity field in February 2007. After passing Pluto and Charon, the craft will be directed toward one more object in the Kuiper Belt. tvb now,tvbnow,bttvb$ q2 \) K8 M' L) h% `2 ]
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Who knows what the probe may find? It has only been traveling for seven months, and two new moons and a dwarf planet have already appeared on its route.
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Ceres, named after the Roman goddess of agriculture, was discovered in 1801 by Giuseppe Piazzi. It was first called a planet, then demoted to asteroid status, and now is called a dwarf planet. The largest object in the asteroid belt between Mars and Jupiter, Ceres is about 600 miles in diameter--almost one-fourth the size of Earth's moon. It completes one orbit around the Sun in about 4.6 Earth years. 5.39.217.764 L' v8 E5 |+ k1 c! Z3 Q" _% H
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These are Hubble Space telescope images that show Ceres rotating a quarter turn.
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Earlier this year NASA canceled, then reinstated, the Dawn mission that is now scheduled to launch in 2007. A probe will be sent on a four-year journey to the minor planet Vesta, where it will spend about a year before being sent to its next target, Ceres, where it will arrive in 2016.

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Another object that is now a dwarf planet is officially named 2003 UB313, but it is better-known as "Xena." It was discovered in 2005 by Michael Brown, Chad Trujillo and David Rabinowitz from images taken in 2003 and is slightly larger than Pluto.

The name Xena comes from the TV series "Xena: Warrior Princess." Its moon is called Gabrielle, named after Xena's sidekick on the show.

The name has gained popularity because the object fits the description of astromer Percival Lowell's Planet X from the early 1900s. But some astronomers object to officially calling it Xena because the planets are supposed to be named after characters from Greek or Roman mythology.

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An International Astronomical Union's committee had proposed a new definition of a planet as an object that orbits the Sun but is massive enough for its own gravity to put it into a spherical shape. Other scientists argued that the three new proposed planets and Pluto were too small and insignificant to be considered full-fledged planets.

The dozen planets would have included Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, Charon, Ceres and Xena.5.39.217.768 z% l, Q" Q, T. f+ Q
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This is an artist's montage of an "expanded" solar system.
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Credit: NASA, ESA, and A. Feild (STScI), J.Y. Li (University of Maryland) and G. Bacon (STScI), H. Weaver (JHU/APL), A. Stern (SwRI), and the HST Pluto Companion Search Team
Credit: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)tvb now,tvbnow,bttvb; `1 K' `& b a7 n& k8 F

評語
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第一個參加天文學追蹤的會員, 多謝你的支持! 剛剛唔記得左每張圖片+1分俾你, 私底下轉左6分俾你啦^^

[ 本帖最後由 jwxie518 於 2006-8-24 04:55 PM 編輯 ]

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