[meteorite-list] 'Plutons' Push Planet Total Up To 12
From: Larry Lebofsky <lebofsky_at_meteoritecentral.com>
Date: Wed Aug 16 06:34:10 2006 Message-ID: <1155724434.44e2f4924be4e_at_hindmost.LPL.Arizona.EDU> Hi Sterling: Have not read all of your emails. The Scotsman released the news early, shame on them. The press found out yesterday at 8:00 am Prauge time and that is 11:00 pm Monday night in California. We (Planetary Sciences Committee) found out Tuesday morning since as the largest group of planetary scientists, we would probably be getting the calls to give our opinion and we needed, as an organization) a "response." We as individuals may not agree with it and may speak it (like apparently Brown is doing even though he was on the IAU committee). However, I will respond to your last comment and what clear is pushing your button (at least this time). We had a report from on of the committee and the decision all has to do with physics. If gravity controls your shape, you may be considered a planet. I have no idea where Brown came up with 50 on their list. This is not official. The Question and Answer release has nine additional TNOs and 3 asteroids as potentially large enough to be in hydrostatic equilibrium (but we do not have enough information at the present time). Vesta is in this group. Picking a size is arbitrary and the committee did not want to do this (say just the size of Mercury or larger or just the size of Pluto or larger). With respect to Pluto and Charon. They both meet the planet criterion (so do a number of planetary satellites including our Moon). However, the center of mass is outside either body (their barycenter). The committee used the same cirterion as is used to define a binary star system. So, we have a binary planetary system! The system may be a bit complicated (do not think so), but it is not arbitary and relies on the physical nature of the object. Why would you just say 2000 km (or 2000 miles or 2000 leagues or 2000 stadia; pick a unit) Larry PS I will go back through your other "comments" and try to respond to them. While not on the committee, I heard one of the committee explain the reasoning and we spent some time in discussing the reasoning. Quoting "Sterling K. Webb" <sterling_k_webb_at_sbcglobal.net>: > Hi, All, > > > A much more detailed piece about the IAU > recommendation in The Boston Globe: > http://www.boston.com/news/science/articles/2006/08/16/nine_no_longer_panel_dec lares_12_planets/ > > It contains an interview with Michael Brown which > is quite interesting. You'd think he'd be all for it, because of > 2003UB313, but instead he says he doesn't favor it: > > "There are 53 objects that meet the panel's criteria and > probably many more to be discovered, according to > Michael Brown, an astronomer at the California Institute > of Technology who discovered 2003 UB313. The total > number of planets, Brown said, could easily climb above > 100. > A new panel of the astronomical union will be charged > with designating planets, and it will be its job to determine > if astronomers have proven that a particular body is > sufficiently round to qualify. > A number of scientists said in interviews that they > expected the new definition would be accepted, but > others, including Brown, opposed the idea. Calling it > 'a big mess,' Brown said he didn't like the complexity > of the system, or the idea of a panel determining > what new planets are." > > Another Committee... > > A check on the figures shows that the diameter of > Charon is just slightly great than 50% of the diameter > of Pluto, so perhaps that's the guideline for defining > a double planet... > > > Sterling K. Webb > ---------------------------------------------------------------- > > ----- Original Message ----- > > From: "Ron Baalke" <baalke_at_zagami.jpl.nasa.gov> > > To: "Meteorite Mailing List" <meteorite-list_at_meteoritecentral.com> > > Sent: Tuesday, August 15, 2006 10:54 PM > > Subject: [meteorite-list] 'Plutons' Push Planet Total Up To 12 > > > > > >> > >> http://news.scotsman.com/scitech.cfm?id=1194292006 > >> > >> 'Plutons' push planet total up to 12 > >> JOHN VON RADOWITZ > >> The Scotsman > >> August 15, 2006 > >> > >> A NEW kind of planet, the "pluton", could soon be taking its place in the > >> Solar System. > >> > >> Astronomers have agreed on a draft proposal for redefining what > >> constitutes a planet. > >> > >> If approved at a meeting underway in the Czech capital, Prague, school > >> science text books will have to be re-written. > >> > >> The new definition would mean there are 12, not nine planets, and more > >> could be added to the list in the future. > >> > >> They include eight "classic" planets - Mercury, Venus, Earth, Mars, > >> Jupiter, Saturn, Uranus and Neptune - Ceres, currently considered an > >> asteroid, and three "plutons," one of which is Pluto. > >> > >> The other plutons are Charon, currently described as a moon of Pluto, > >> and the newly-discovered object 2003 UB313, which has not been named > >> officially, but is nicknamed Xena. > >> > >> Ceres is the largest object in the asteroid belt between Mars and > >> Jupiter, and like a planet is spherical in shape. > >> > >> A resolution to accept the new planet definition will be voted on by > >> members of the International Astronomical Union (IAU) next Thursday, > >> 24 August. If passed, the days of simply learning the names of the > >> nine planets will be over for the world's schoolchildren. In future, > >> many more planets could join the Sun's family as other plutons are > >> discovered. > >> > >> A dozen "candidate planets" are already on the IAUs "watchlist". They > >> include Varuna, Quaor and Sedna, all Pluto-like objects residing > >> within a region on the fringe of the Solar System known as the > >> "Kuiper Belt". > >> > >> Plutons differ from classical planets in that they have orbits round > >> the Sun that take longer than 200 years to complete, and their orbits > >> are highly-tilted and non-circular. > >> > >> All these characteristics suggest that they have an origin different > >> from that of classical planets. > >> > >> The IAU has taken two years working out the differences between planets > >> and smaller Solar System bodies such as comets and asteroids. > >> > >> IAU president Professor Ron Ekers said: "Modern science provides much > >> more knowledge than the simple fact that objects orbiting the Sun > >> appear to move with respect to the background of fixed stars. > >> > >> "For example, recent new discoveries have been made of objects in the > >> outer regions of our Solar System that have sizes comparable to and > >> larger than Pluto. > >> > >> "These discoveries have rightfully called into question whether or not > >> they should be considered as new 'planets'." > >> > >> According to the new draft definition, two conditions must be satisfied > >> for an object to be called a "planet". > >> > >> First, the object must be in orbit around a star, while not itself > >> being a star. Second, and most importantly, it must be massive enough > >> for its own gravity to pull it into a nearly spherical shape. > >> > >> The IAU, responsible for the naming of planets and moons since 1919, > >> set up a Planet Definition Committee (PDC) to consider the problem. > >> Committee member Professor Richard Binzel said: "Our goal was to find a > >> scientific basis for a new definition of planet, and we chose gravity > >> as the determining factor. > >> > >> "Nature decides whether or not an object is a planet." > >> > >> Mnemonic needed > >> > >> IF ASTRONOMERS decide to change the number of planets in our solar > >> system then piles of science textbooks will have to be rewritten. > >> > >> Generations of children have learned the names of the planets using > >> mnemonics, listing the celestial bodies in their order from the Sun. > >> > >> "My Very Eager Mother Just Sent Us Nine Pies" is one popular aide > >> memoir, helping students to remember Mercury, Venus, Earth, Mars, > >> Jupiter, Saturn, Uranus, Neptune and Pluto. > >> > >> Other useful phrases include "Make Very Easy Mash - Just Squash Up > >> New Potatoes" and "My Very Easy Method Just Showed Us Nine Planets". > >> > >> > >> ______________________________________________ > >> Meteorite-list mailing list > >> Meteorite-list_at_meteoritecentral.com > >> http://six.pairlist.net/mailman/listinfo/meteorite-list > >> > > > > > > ______________________________________________ > > Meteorite-list mailing list > > Meteorite-list_at_meteoritecentral.com > > http://six.pairlist.net/mailman/listinfo/meteorite-list > > > > > ______________________________________________ > Meteorite-list mailing list > Meteorite-list_at_meteoritecentral.com > http://six.pairlist.net/mailman/listinfo/meteorite-list > -- Dr. Larry A. Lebofsky Senior Research Scientist Co-editor, Meteorite "If you give a man a fish, Lunar and Planetary Laboratory you feed him for a day. 1541 East University If you teach a man to fish, University of Arizona you feed him for a lifetime." Tucson, AZ 85721-0063 ~Chinese Proverb Phone: 520-621-6947 FAX: 520-621-8364 e-mail: lebofsky_at_lpl.arizona.eduReceived on Wed 16 Aug 2006 06:33:54 AM PDT |
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