Pluto is no longer a planet?

Question

why?!

Answer 1

the international astronomical union has defined three new terms to categorize the bodies in the solar system.

(1) A classical 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.

(3) All other objects orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".

http://www.iau2006.org/mirror/www.iau.org/iau0602/index.html

this does not change anything about pluto or the solar system, but it does change the language to ft observation. this corrects the mistake of categorizing pluto as a planet initially.

Answer 2

When it was discovered in 1930, nobody knew that objects like Pluto were pretty common outside the orbit of Neptune. So it was a bad decision then to call it a "planet." Since then, many similar bodes have been found in its vicinity, including its moon Charon, other large bodies like Sedna, and even a body larger than Pluto (2003UB313).

A very similar renaming happened to Ceres (between the orbits of Mars and Jupiter) back in 1801. First classified as a planet, it was soon discovered to be the first among a bunch of similar objects, and it was re-classified as an asteroid.

The problem was that there has never been, until now, a firm definition by astronomers as to what a "planet" is. The discovery of UB313 forced the issue.

So the IAU had a choice. If they defined "planet" to include Pluto, then there is no reason they could not include UB313, and Charon, and Ceres, and then additional asteroids like Vesta and Pallas, and other trans-Neptunian objects like Sedna, Quauoar. There are as many as 53 objects we know of that would fall into a similar category as Pluto.

To me, a definition that results in 53 planets, and always growing, would have been worse. (You worry about schoolkids and mnemonics? ... start adding names like Ceres, Charon, Xena ... and then next year they have to add (and pronounce) Quaoar ... and the year after that we add Vesta, Pallas, Ixion Orcus, Varuna etc. etc. to the things you have to memorize.)

The PR-sensitive thing to do would have been to simply declare Pluto as a special exception to the new definition. Unfortunately, that's just bad science ... you don't grant things "honorary" status just because of historical sentiment. A scientific definition applied inconsistently just erodes confidence that scientists know what their talking about.

Another thing to consider ... scientists are also thinking about the new planets we are starting to find orbiting other stars. They need to have a classification system that works well into the future.

So as much as I am sentimentally saddened by the news ... it is the scientifically correct thing to do.

Answer 3

No pluto is not longer a part of our solar system. At the recent space and astronomy convention they elected to redefine the definition of a planet. and pluto does not qualify for that. and neither does the other 3 that were questionable to bein added. pluto is interfering with neptunes orbit which makes it a dwarf planet. although there is a asteroid that is very large in the asteroid belt that may be considered large enough to be call a planet.

Answer 4

because scientist say its orbit interferes with neptunes orbit. so now its a dwarf planet

Answer 5

NO HE IS A DOG AT DISNEYLAND