From: "Strong, Lee" <strongl at sddc.army.mil>
To: "WSFAList (E-mail)" <WSFAList at keithlynch.net>
Subject: [WSFA] Planets
Date: Mon, 15 Mar 2004 10:28:56 -0500
Reply-To: WSFA members <WSFAlist at keithlynch.net>

    Fellow Terrans, various members of the WSFA Chat List are discussing
the recent discovery of "tenth planet" Sedna and how to classify a body as a
planet.  Current astronomical thinking is that any dark object orbiting a
star is a "planet" and that any dark object orbiting a planet is a
"satellite", as is a dark object orbiting a satellite  The distinction
between Jupiter and Ceres is "major planet" versus "minor planet."  So
Kuiper Belt Objects, including Pluto, are planets, just minor ones.  A
further distinction is "artificial" versus "natural" which takes care of
Keith's Apollo rocket stage (artificial minor planet Apollo # Stage #).
    The distinction between "major" and "minor" is fundamentally
arbitrary and appears to be a holdover from the days of naked eye astronomy
when size of object governed its visibility.  Ceres is not visible to the
unaided human eye and therefore it is classifed as minor.  As readers of
Weinbaum's "The Red Peri" know, Pluto was once considered to be much larger
and old habits die hard.
    Since astronomers have identified over 10,000 planets of all sizes
in the Sol System, I am looking forward to the mnemonic that Adrienne will
construct to help us remember them all and in their proper orbits!