A question about the 冥王星.
Why is Pluto(冥王星) no longer a planet(行星)? How come it is dimolished? Have anybody got any websites?
- ?Lv 71 十年 前最佳解答
Main article: 2006 redefinition of planet
The debate came to a head in 2006 with an IAU resolution that created an official definition for the term "planet". According to this resolution, there are three main conditions for an object to be considered a 'planet':
The object must be in orbit around the Sun.
The object must be massive enough to be a sphere by its own gravitational force. More specifically, its own gravity should pull it into a shape of hydrostatic equilibrium.
It must have cleared the neighbourhood around its orbit.
Pluto fails to meet the third condition. The IAU further resolved that Pluto be classified in the simultaneously created dwarf planet category, and that it act as prototype for a yet-to-be-named category of trans-Neptunian objects, in which it would be separately, but concurrently, classified.
There has been resistance amongst the astronomical community towards the reclassification, dubbed the "Great Pluto War" by some astronomers.Alan Stern, principal investigator with NASA's "New Horizons" mission to Pluto, has publicly derided the IAU resolution, stating that "the definition stinks, for technical reasons." Stern's current contention is that by the terms of the new definition Earth, Mars, Jupiter and Neptune, all of which share their orbits with asteroids would be excluded.However, his own published writing has supported the new list of planets, as "our solar system clearly contains" eight planets that have cleared their neighbourhoods.Marc W. Buie of the Lowell observatory has voiced his opinion on the new definition on his website and is one of the petitioners against the definition. Others have supported the IAU. Mike Brown, the astronomer who discovered Eris, said "through this whole crazy circus-like procedure, somehow the right answer was stumbled on. It’s been a long time coming. Science is self-correcting eventually, even when strong emotions are involved."
Among the general public, reception is mixed amidst widespread media coverage. Some have accepted the reclassification, while some are seeking to overturn the decision, with online petitions urging the IAU to consider reinstatement. A resolution introduced by some members of the California state assembly light-heartedly denounces the IAU for "scientific heresy," among other crimes. The U.S. state of New Mexico's House of Representatives passed a resolution declaring that, in honour of Tombaugh, a longtime resident of that state, Pluto will always be considered a planet while in New Mexican skies, with March 13th being known as "Pluto Planet Day". Others reject the change for sentimental reasons, citing that they have always known Pluto as a planet and will continue to do so regardless of the IAU decision.
The verb "pluto" (preterite and past participle: "plutoed") was coined in the aftermath of the decision. In January 2007, the American Dialect Society chose "plutoed" as its 2006 Word of the Year, defining "to pluto" as "to demote or devalue someone or something", an example being "as happened to the former planet Pluto when the General Assembly of the International Astronomical Union decided Pluto no longer met its definition of a planet."資料來源： 維基
- guru．1．2．3Lv 71 十年 前
In very simple term (NOT from Wikipedia), scientists decided that Pluto is no longer a " Planet " but DEMOTED as " Dwarf Planet " in our Solar System.
(Demoted NOT dimolished as you said in the question).
Reason is that Pluto does not meet the criteria of being a Planet under the modified definition on 24 Aug 2006. WHY ? It is because Pluto has not cleared the neighborhood around its orbit and it cuts into the orbit of Neptune and Uranus.
Thus, we now got only " 8 Planets " in our solar system.
*** Definition of a Planet
A planet is any object in orbit around the Sun with a diameter greater than 2000 km
A planet is any object in orbit around the Sun whose shape is stable due to its own gravity.
A planet is any object in orbit around the Sun that is dominant in its immediate neighborhood. (has cleared neighborhood around its orbit)
Websites (from News media and from NASA)
Scientists decide Pluto is no longer a planet
Pluto loses status as a planet
Pluto Is Demoted to Dwarf Planet
Solar System Shrinks with Pluto's Demotion
Eight Planets and New Solar System Designations (from NASA)
NASA Solar System Exploration
### others pls do not copy
2007-06-09 12:09:58 補充：
.Written and typed by my own (not just copy and paste from Wikipedia).資料來源： NASA