04-05-2005 05:36									#61
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quote: Originally posted by Kuciwalker No. It's a chunk of rock in the middle of nowhere.

Chances are it would be classified as an ejected planet, since planet-sized chunks of rock can apparently only be formed in a star's circumstellar disk.

Much like this one:

http://hubblesite.org/newscenter/ne...leases/1998/19/

	04-05-2005 10:44									#62
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quote: Originally posted by chegitz guevara Incorrect. Black holes radiate nothing, hence the term, black hole. The accretion disks around black holes, however, radiate massive amounts of energy.

Hawking radiation and quantum mechanical effects. This is the reason why those particle sized black holes they are trying to make will never swallow up the earth (they decay in a shower of particles in about 10^-27 seconds).

Of course, that's all just a theory.

	04-05-2005 13:28									#63
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quote: Originally posted by Az It's a silly definition. If, for example, one would find a celestial body the size of earth, venus, or mars, drifting in space, not calling it a planet would be completely rediculous, IMHO.

It seems there is no standard definition of a 'Planet'.
Making some internet search, I came across this definition http://exoplanets.org/defn.html

quote: A ``planet'' is an object that has a mass between that of Pluto and the Deuterium-burning threshold and that forms in orbit around an object that can generate energy by nuclear reactions.

But more interresting is this one:
http://www.ciw.edu/IAU/div3/wgesp/

quote: The WGESP (Working Group on Extrasolar Planets) has developed a Working Definition of a "planet", subject to change as we learn more about the population of very low mass companions. Emphasizing again that this is only a working definition, subject to change as we learn more about the census of low-mass companions, the WGESP has agreed to the following statements: 1) Objects with true masses below the limiting mass for thermonuclear fusion of deuterium (currently calculated to be 13 Jupiter masses for objects of solar metallicity) that orbit stars or stellar remnants are "planets" (no matter how they formed). The minimum mass/size required for an extrasolar object to be considered a planet should be the same as that used in our Solar System. 2) Substellar objects with true masses above the limiting mass for thermonuclear fusion of deuterium are "brown dwarfs", no matter how they formed nor where they are located. 3) Free-floating objects in young star clusters with masses below the limiting mass for thermonuclear fusion of deuterium are not "planets", but are "sub-brown dwarfs" (or whatever name is most appropriate). These statements are a compromise between definitions based purely on the deuterium-burning mass or on the formation mechanism, and as such do not fully satisfy anyone on the WGESP. However, the WGESP agrees that these statements constitute the basis for a reasonable working definition of a "planet" at this time. We can expect this definition to evolve as our knowledge improves.