Strength of Materials

On February 27, 2003, I posed a question to this group (sci.physics),
asking who had worked out that objects of sufficient size will collapse
into roughly spherical shapes under the force of their own gravity. No
one here could tell me the answer.

Now, the International Astronomical Union (IAU) has made the definition
of a planet contingent on this physical fact that some on this forum at
the time actually denied existed.

"In short, a 'planet' is now defined as 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."


"Planetary News: Pluto (2006): Pluto Gets the Boot - Solar System
Shrinks to 8 Planets"
http://planetary.org/news/2006/0824_Pluto_Gets_the_Boot__Solar_System.html

.

Relevant Pages

  • Re: New "Planet" Definition: How "Round" Is "Round" ???
    ... A planet is a celestial body that is in orbit around ... the Sun, has sufficient mass for its self-gravity to overcome ... rigid body forces so that it assumes a hydrostatic equilibrium ...
    (rec.arts.sf.written)
  • Re: ambiguity-free planetary classification
    ... " A Planet is a Celestial body that has sufficient mass for its ... The Aliens are probably scratching their heads wondering whether they live ...
    (sci.space.policy)
  • Re: HOWTO create base + devel package from source ?
    ... so what is pluto now?! ... It's now a 'dwarf planet'. ... cleared the neighbourhood around its orbit. ...
    (alt.os.linux.suse)
  • Re: Pluto loses status as a planet
    ... IAU does not have the authority to decide that. ... If English speakers start using the word "planet" ... The new rules for a planet state: "a celestial body that is in orbit ... rigid body forces so that it assumes a ... ...
    (sci.physics)
  • Re: "Pluto Now Called a Plutoid"
    ... "A planet is a celestial body that is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium shape, and has cleared the neighbourhood around its orbit." ... So yes, it would likely be called a planet, even under the IAU's definition. ... a planet 70 percent as massive as the Earth _would_ clear its region in the Kuiper belt. ... It would be approximately as capable of clearing objects from its orbit as Mars is, and Mars is considered a planet. ...
    (rec.arts.sf.science)