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Posting-Version: version B 2.10.2 12/4/84; site seismo.UUCP
Path: utzoo!watmath!clyde!bonnie!akgua!gatech!seismo!rivers
From: rivers@seismo.UUCP (Wilmer Rivers)
Newsgroups: net.astro
Subject: re:planet discovered around another star
Message-ID: <6483@seismo.UUCP>
Date: Thu, 20-Dec-84 08:43:00 EST
Article-I.D.: seismo.6483
Posted: Thu Dec 20 08:43:00 1984
Date-Received: Sat, 22-Dec-84 02:22:06 EST
References: <1352GMS@PSUVM>
Organization: Center for Seismic Studies, Arlington, VA
Lines: 29

In article <1352GMS@PSUVM>, GMS@PSUVM.BITNET writes:
> I believe that there is some controversy surrounding the apparant
> discovery of a 'planet' orbiting another star in Ophiuchus.  The controversy
> is not concerning the object itself, for it is most certainly there, but
> rather what to call it.
> 
> To be rather picky about names, this object should be termed a 'brown
> dwarf' rather than a planet.  Current theories of solar system formation
> include the probable existance of such objects.  It could be still
> condensing, and may one day shed its outer atmosphere to shine (albeit
> faintly) as a red dwarf star.
Has the IAU, or any other such body, adopted a formal definition of
what is a "star", and what is a "planet"? This "brown dwarf" definition
seems to rest on the distinction that it is a star because fusion is
going on in the core. However, it should be noted that deuterium fusion
takes place at a much lower temperature than does hydrogen fusion, and
it has been speculated (sorry, I don't remember the references) that
Jupiter may have had enough energy released by gravitational contraction
to burn deuterium at one time. Even now, Jupiter emits more energy than
it receives from the sun; does this qualify it to be a "star", albeit
one that has entered a post-fusion "dwarf" stage ? The intuitive dis-
tinction between stars and planets is that stars are (ionized) gas,
whereas planets have a solid (Moon), liquid (Enceladus ?), or metallic
(Jupiter ?) core. Even this idea, however, does not correctly consider
the interiors of those dwarfs which are (or which at one time were)
unarguably "stars" but which are now cool. [Note that in the limiting
case of nuclear matter, neutron stars have cm-tall "mountains" and
undergo "starquakes".] So just what is the official distinction
between stars and planets ?