IAU to Decide "Planet" Definition... Jun 13, 2006 14:46:30 GMT -6
Post by Chicago Astronomer Joe on Jun 13, 2006 14:46:30 GMT -6
Definition of 'Planet' Expected in September
Historians and educators have joined astronomers in an effort to break a deadlock on contentious discussions over a definition for the word planet.
A decision is expected in September, but history suggests rewriting the textbooks could be more challenging than finding tiny new worlds at the edge of the solar system.
The International Astronomical Union (IAU) is expected to propose wording to delineate planets from other small, round objects at its 12-day General Assembly meeting in Prague this August. The proposal will be based on recommendations from a newly formed committee that includes experts outside the realm of astronomy tasked to break a deadlock in earlier committee discussions.
Depending on the outcome of a separate controversial procedural issue—whether IAU members should be allowed to vote on such things—astronomers might then have the chance to weigh in on the definition later.
Some might think it ironic that the world's governing body for astronomy does not have a definition for planet.
The problem stretches back to the late 1990s, when astronomers began discovering Pluto-like objects in the distant reaches of our solar system.
All the newfound worlds—there are several known now—were until recently smaller than Pluto, but they are round and orbit the Sun, two characteristics that had for centuries been sufficient for the implicit definition of planet. The hitch: These small objects are typically on wild, elongated orbits that stretch well above and below the main plane of the solar system where eight of the traditional planets travel (Pluto has a wild orbit, too, which is one reason many astronomers do not consider it a planet anymore).
So what to call them? Astronomers have been arguing about it in earnest since 1999.
The controversy came to a head with the July 2005 announcement of 2003 UB313, an object roughly the size of Pluto that orbits the Sun beyond Neptune. The object's discoverer, Mike Brown of Caltech, has argued it should be called a planet.
But other astronomers say that if planethood is bestowed upon 2003 UB313, then several similar way-out bodies should gain the same status, and the number of planets in our solar system could ultimately climb into the thousands as search technology improves.
Neither Bowell nor Boss knows what exactly might happen next, however. Nor does Brian Marsden, leader of the Minor Planet Center where newfound objects are catalogued. Marsden was also on the first definition committee.
"The new committee is supposed to recommend what 'should be done' about Pluto, 2003 UB313 and other 'largish' small bodies, but it is not clear that what they decide will depend on mass," Marsden told SPACE.com.
Marsden said it's also unclear how the IAU will reach an ultimate resolution.
"The IAU made the interesting policy decision in 2003 to disenfranchise its members, and they were therefore not allowed to vote on 'scientific matters' (such as what a planet is) at the last plenary General Assembly session at the Sydney meeting [in 2003]," Marsden said. "There are rumors that there may be an administrative decision to re-enfranchise us at the first of the upcoming plenary sessions this August in Prague—so that suggested vote might be possible at the second."
That is indeed the plan, IAU General Secretary Oddbjorn Engvold explained yesterday. The advisory Committee is scheduled to meet June 30, Engvold said by email.
Full story here from Space.com: www.space.com/scienceastronomy/060608_planet_definition.html
Does Pluto get knocked down or do the many objects out there get elevated to planet status.
Quite a pondering...