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Response to DreamGypsy (Original post)

Thu May 30, 2013, 08:08 PM

2. Surprise, 1998 QE2 is a "planet" according to the In't Astrological Union (IAU) definition.

Scroll down to the bottom of the post here: http://www2.ess.ucla.edu/~jlm/epo/planet/planet.html

Apparently it has sufficient mass to retain its own satellite, which is surprising. Both of them are soon to be visiting our part of the solar system.

The fact that it has a moon shows that 1998 that it has "cleared its neighborhood" of other objects, and is is a full-fledged planet, according to another IAU definition: http://en.wikipedia.org/wiki/Clearing_the_neighbourhood

"Clearing the neighbourhood of its orbit" is a criterion for a celestial body to be considered a planet in the Solar System. This was one of the three criteria adopted by the International Astronomical Union (IAU) in its 2006 definition of planet.[1]

In the end stages of planet formation, a planet will have "cleared the neighbourhood" of its own orbital zone, meaning it has become gravitationally dominant, and there are no other bodies of comparable size other than its own satellites or those otherwise under its gravitational influence. A large body which meets the other criteria for a planet but has not cleared its neighbourhood is classified as a dwarf planet. This includes Pluto, which shares its orbital neighbourhood with Kuiper belt objects such as the plutinos. The IAU's definition does not attach specific numbers or equations to this term, but all the planets have cleared their neighbourhoods to a much greater extent than any dwarf planet, or any candidate for dwarf planet.

The phrase may be derived from a paper presented to the general assembly of the IAU in 2000 by Alan Stern and Harold F. Levison. The authors used several similar phrases as they developed a theoretical basis for determining if an object orbiting a star is likely to "clear its neighboring region" of planetesimals, based on the object's mass and its orbital period.[2]

Clearly distinguishing "planets" from "dwarf planets" and other minor planets had become necessary because the IAU had adopted different rules for naming newly discovered major and minor planets, without establishing a basis for telling them apart. The naming process for Eris stalled after the announcement of its discovery in 2005, pending clarification of this first step.


This could change the way we view planetary systems, or that moon could just be an interstellar craft in a parking orbit.

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DreamGypsy May 2013 OP
CaliforniaPeggy May 2013 #1
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CaliforniaPeggy May 2013 #4
LineReply Surprise, 1998 QE2 is a "planet" according to the In't Astrological Union (IAU) definition.
leveymg May 2013 #2
DreamGypsy May 2013 #6
leveymg May 2013 #7
DreamGypsy May 2013 #9
Angleae May 2013 #12
leveymg May 2013 #14
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Jackpine Radical May 2013 #5
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