Pluto's fifth moon discovered

[barx1963 (Malcolm)]

Once again Warren, as per my previous posts, the definition does not require "complete" clearing of the orbital zone, only clearing of objects of comparable size. Unless I am mistaken there are no objects comparable to Earths size in our zone (for example!).
Several minor bodies have satellites, the asteroid Ida has a moon named Dactyl, the dwarf planet Haumea has 2 moons and the dwarf planet Eris has 1 called Dysnomia. In any case, presence of satellites is not relevant as Mercury and Venus have no natural satellites.
Further on a historical note, in ancient Greece the planets included the Sun and Moon as all bodies than moved in the heavens were called planets. So we should not feel squeamish about updating our definitions.

Cheers

Malcolm

Originally Posted by supernova1965

This is my point Pluto is no asteroid it has 5 moons it has gravitational control in its region it is spherical no planet has completely cleared its orbit so lets just say there are no planets because strict application of the new rule does just this to me this is just as silly as saying that Pluto isn't a planet. How many objects truly similar to Pluto are there I haven't heard of any objects out there with moons like Pluto?

[supernova1965 (Warren)]

A planet is 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 neighbourhood around its orbit.


I understand your point but the defination as posted above taken from the IAU site doesn't state has cleared most of the objects in its orbit it says simply has cleared the neighbourhood around its orbit. They should change it to say cleared the orbit of significant objects this the only point that disqualifies Pluto as a planet so to disqualify Pluto this needs to be amended. Going by this one point as written there would be a lot less planets in our solar system.

[TrevorW]

Warren this is worth a look

http://www.universetoday.com/13573/w...nger-a-planet/