When did pluto become a dwarf planet?
6 posts
• Page 1 of 1
When did pluto become a dwarf planet?
by reginald » Mon Aug 17, 2009 11:30 am
On August 24, 2006 the IAU pronounced it a dwarf planet
- reginald
- Posts: 73
- Joined: Fri Aug 07, 2009 2:42 pm
When did pluto become a dwarf planet?
by eldred89 » Mon Aug 17, 2009 12:04 pm
How many planets are in the Solar System? This popular question now has a new formal answer according the International Astronomical Union (IAU): eight. Last week, the IAU voted on a new definition for planet and Pluto did not make the cut. Rather, Pluto was re-classified as a dwarf planet and is considered as a prototype for a new category of trans-Neptunian objects. The eight planets now recognized by the IAU are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Solar System objects now classified as dwarf planets are: Ceres, Pluto, and the currently unnamed 2003 UB313. Planets, by the new IAU definition, must be in orbit around the sun, be nearly spherical, and must have cleared the neighborhood around their orbits. The demotion of Pluto to dwarf planet status is a source of continuing dissent and controversy in the astronomical community.
- eldred89
- Posts: 75
- Joined: Fri Aug 07, 2009 3:32 pm
When did pluto become a dwarf planet?
by moulton » Mon Aug 17, 2009 12:58 pm
2006: IAU classification
Main article: 2006 definition 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':
1. The object must be in orbit around the Sun.
2. 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.
3. It must have cleared the neighbourhood around its orbit.
Pluto fails to meet the third condition, since its mass was only 0.07 times that of the mass of the other objects in its orbit (Earth's mass, by contrast, is 1.7 million times the remaining mass in its own orbit). The IAU further resolved that Pluto be classified in the simultaneously created dwarf planet category, and that it act as the prototype for the plutoid category of trans-Neptunian objects, in which it would be separately, but concurrently, classified.
On September 13, 2006, the IAU included Pluto, Eris, and the Eridian moon Dysnomia in their Minor Planet Catalogue, giving them the official minor planet designations "(134340) Pluto", "(136199) Eris", and "(136199) Eris I Dysnomia". If Pluto had been given a minor planet name upon its discovery, the number would have been a little over a thousand rather than over 100,000. The first minor planet to be found after Pluto was 1164 Kobolda, a month later.
There has been some resistance within the astronomical community toward the reclassification. 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 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. His other claim is that because less than five percent of astronomers voted for it, the decision was not representative of the entire astronomical community. 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."
The ongoing debate over the status of Pluto continues to be acknowledged by the Jet Propulsion Laboratory which, as recently as January 2008, continued to reference it on JPL Photojournal webpages dedicated to Pluto. Researchers on both sides of the debate gathered on August 14-16, 2008 at The Johns Hopkins University Applied Physics Laboratory for a conference that included back-to-back talks on the current IAU definition of a planet. Entitled "The Great Planet Debate", the conference published a post-conference press release indicating that scientists could not come to a consensus about the definition of a planet. Just before the conference, on June 11, 2008, the IAU announced in a press release that the term "plutoid" would henceforth be used to describe Pluto and other objects similar to Pluto which have an orbital semimajor axis greater than that of Neptune and enough mass to be of near-spherical shape.
Main article: 2006 definition 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':
1. The object must be in orbit around the Sun.
2. 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.
3. It must have cleared the neighbourhood around its orbit.
Pluto fails to meet the third condition, since its mass was only 0.07 times that of the mass of the other objects in its orbit (Earth's mass, by contrast, is 1.7 million times the remaining mass in its own orbit). The IAU further resolved that Pluto be classified in the simultaneously created dwarf planet category, and that it act as the prototype for the plutoid category of trans-Neptunian objects, in which it would be separately, but concurrently, classified.
On September 13, 2006, the IAU included Pluto, Eris, and the Eridian moon Dysnomia in their Minor Planet Catalogue, giving them the official minor planet designations "(134340) Pluto", "(136199) Eris", and "(136199) Eris I Dysnomia". If Pluto had been given a minor planet name upon its discovery, the number would have been a little over a thousand rather than over 100,000. The first minor planet to be found after Pluto was 1164 Kobolda, a month later.
There has been some resistance within the astronomical community toward the reclassification. 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 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. His other claim is that because less than five percent of astronomers voted for it, the decision was not representative of the entire astronomical community. 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."
The ongoing debate over the status of Pluto continues to be acknowledged by the Jet Propulsion Laboratory which, as recently as January 2008, continued to reference it on JPL Photojournal webpages dedicated to Pluto. Researchers on both sides of the debate gathered on August 14-16, 2008 at The Johns Hopkins University Applied Physics Laboratory for a conference that included back-to-back talks on the current IAU definition of a planet. Entitled "The Great Planet Debate", the conference published a post-conference press release indicating that scientists could not come to a consensus about the definition of a planet. Just before the conference, on June 11, 2008, the IAU announced in a press release that the term "plutoid" would henceforth be used to describe Pluto and other objects similar to Pluto which have an orbital semimajor axis greater than that of Neptune and enough mass to be of near-spherical shape.
- moulton
- Posts: 68
- Joined: Fri Aug 07, 2009 2:42 pm
When did pluto become a dwarf planet?
by marceau » Mon Aug 17, 2009 1:05 pm
On August 24, 2006 the IAU voted to define a planet and dwarf planet. Pluto was bumped into the latter category. A pretty good explanation of the events is at the link below, but it leaves out much of the anti-American bickering.
- marceau
- Posts: 59
- Joined: Fri Aug 07, 2009 2:42 pm
When did pluto become a dwarf planet?
by huxley » Mon Aug 17, 2009 2:02 pm
about 4 billlion years ago :p
- huxley
- Posts: 74
- Joined: Fri Aug 07, 2009 2:42 pm
When did pluto become a dwarf planet?
by reginald » Mon Aug 17, 2009 2:34 pm
About 3 years ago, IIRC.
Doug
Doug
- reginald
- Posts: 73
- Joined: Fri Aug 07, 2009 2:42 pm
6 posts
• Page 1 of 1
Return to Planets & Solar System
Who is online
Users browsing this forum: No registered users and 1 guest