Sunday, August 27, 2006

Back to the doghouse

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If you don't clear your neighborhood, you just can't be a planet. It works on so many levels. The redefinition of "planet" last week by the International Astronomical Union states that a planet is a celestial body that is in orbit around the sun, is in hydrostatic equilibrium (nearly round shape) and has "cleared the neighborhood" around its orbit. This sends Pluto back to the doghouse.

Oddly, there was the possibility of keeping pluto and including three more celestial bodies in the list of planets in our solar system at the IAU conference. The matter came to a head with the need to categorize and name the recently-discovered trans-plutonic object 2003 UB313, which, being larger than Pluto, was thought to be equally deserving of the status of "planet". In its original form, the redefinition would have kept Pluto as a planet and recognized three new planets: Ceres--a large asteroid between Mars and Jupiter, Charon--a moon of Pluto or bi-planetary system, and 2003 UB313 (often called "Xena"). It was presumed that, after more observation and discussion, astronomers would accept more objects in the solar system as meeting the new definition. On August 22, however, the original redefinition (which recognized twelve solar system planets, including Pluto), was dealt a fatal blow in two open IAU meetings.

The final decision has been criticised for several reasons. First, the lead scientist on NASA's robotic mission to Pluto, Dr Alan Stern, contends that Earth, Mars, Jupiter and Neptune have also not fully "cleared their orbital zones" either. Earth orbits with 10,000 near-Earth asteroids. Jupiter, meanwhile, is accompanied by 100,000 Trojan asteroids on its orbital path. "If Neptune had cleared its zone, Pluto wouldn't be there," he added.

Second, many astronomers were unhappy that they were left out of the final discussion. The votes were cast on the last day of the Prague conference when many of the 2,500 attendants had already left. As only 424 voters participated it is debatable that this represents a consensus.

I wouldn't buy a new science textbook just yet.
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2 comments:

Kraft said...

I wonder if the Pluto debate/vote was on the agenda. If so, I don't believe the people who left can grumble about the outcome.

What is quorum for the group? If they still grumble, perhaps they should look at their structure to determine why was a vote still carried out with so many absent.

Timotheos Prologizes said...

I had not thought about the quorum issue. Would a quorum only be needed to open the meeting, or would it be required throughout to transact business?

I suspect that the definition and number of planets will not last for the long term.