August 24, 2006 7:40 AM PDT
Pluto: And then there were eight
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New planet discovered in Milky Way
January 25, 2006
The celestial body, long known as one of the nine planets of the solar system, will now be considered a "dwarf planet," the General Assembly of the 2006 International Astronomical Union ruled in a vote Thursday in Prague, Czech Republic.
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune will be defined as "classical planets."
Three other bodies had been contending for planetary status as well: Ceres, the largest-known asteroid; "Xena," the nickname for 2003 UB313; and Charon, which has been considered Pluto's moon.
Ceres and "Xena" will now share "dwarf planet" status with Pluto. Charon, it has been concluded, will be grouped with "small solar-system bodies."
The IAU said in a statement on Thursday that the definition for planet is now officially "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."
"More dwarf planets are expected to be announced by the IAU in the coming months and years,"a ccording to the IAU statement. "Currently, a dozen candidate dwarf planets are listed on IAU's dwarf planet watchlist, which keeps changing as new objects are found and the physics of the existing candidates becomes better-known."
About 2,500 members of the IAU, a community of astronomers from around the world, have been meeting since late last week to debate and vote on a series of resolutions that include definitions of solar-system bodies. The IAU General Assembly is held every three years. This session, four terrestrial bodies in particular have been the focus of the debate--the most prominent being Pluto, which was discovered in 1930.
Varying proposals from IAU members included referring to these smaller terrestrial bodies in different areas of the solar system as "planetoids" and "trans-Neptunian objects." Another proposal referred to the smaller objects as "plutonian objects." Yet another proposed the idea of a hierarchy of "planets," "dwarf planets" and "small solar-system bodies," according to the IAU. Still others wanted to keep Pluto as a planet but come up with alternatives for the other three.
IAU President Ron Ekers and other members of the IAU board are expected to hold a press conference Thursday on the final outcome of all the resolution votes in Prague.
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As for the way the debate went - it started well, but then it became pure sophistry! Any decision was going to be arbitrary, lines have to be drawn somewhere.
A compromise to include Pluto, Xena and Ceres but not Charon was easy or can astronomers not do simple arithmetic? I can and here's a clue Barycentre or >50% Mass similar measurements different arbitrary line, there'd be no Planet Charon based on Mass, though personally if its round I'd have it - I'd even include Moons of other planets, but thats a whole other debate. As for the "'our Moon moving outwards and becoming a planet so what would we call it?' objection" (assuming the sun didn't expand first and we were still here several billion years from now to care)I suggest a good name would be "the Moon". I take it the "top" astronomers will now want to downgrade eighty or so elements from the periodic table because after all there are too many to learn, and some are more important than others, or how about the month of February, it acts very odd for a calendar month? Lastly the 'classical planets' are - and always will be - the Sun, the Moon, Mercury, Venus, Mars, Jupiter and Saturn - find another word smartasses!
In short have as many divisions of planets as required for clarity, but astronomers are supposed to be clever people (I would have thought so but apparently not), context is a wonderful thing.
that it hasn't cleared its "neighborhood," why is NEPTUNE still a
planet?
thing alone. How many years is it we've gone without a definition
for 'planet' and done just fine? 300 years? 400 years? 500 years?
Why can't they just keep doing it on a case by case basis or
something like they've done for however long?
Not that I think it matters for the general public. Those that want
to agree with the council of astronerds will change the way they
think of Pluto, those that want to think of Pluto as a planet will
continue to do so, not giving a rip if someone else says that
Pluto isn't a planet. Or doing it out of habit. I for one will
continue to refer to Pluto as a planet (and saying "whatever"
whenever someone tries to correct me).
As for Plutos moon, Charon, I don't get why that would be up for
consideration anyways.
It orbits Pluto. It's a moon.
You are more than welcome to still call it a planet if you like.
bodies in the Solar system! How does the President of Mars feel
about this important decision? HELLO! A bunch of "scientists"
who know NOTHING about Pluto (or maybe some of them went
there and can claim something with certainty?) decided to
change the definition of the word they came up with in the first
place, completely arbitrarily. They travelled to three conferences
in very nice places to do so. They still know nothing and their
decision and nomenclature are still meaningless, but DAMN,
they have cool jobs for geeks whose top love affair is that with
Xena!
eom
- It's the (who say so)
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by Earl
August 26, 2006 5:37 PM PDT
- Who ever has the say so, Says it & it becomes So.
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