how to define planets

[MeteorWayne]

<i>classifying animals by their size , Or indeed where they live, whether it be on land (orbiting a planet) or in the sea (orbiting a star). </i><br /><br />Which makes sense to me.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[rhm3]

Totally agree about the term moon. A moon should be a gravitationally-rounded spheroid orbiting another gravitationally-rounded spheroid (non-fusor). Basically a "planet" orbiting a planet. The irregular objects orbiting planets can be called moonoids...kind of how all irregular objects obriting stars are planetoids.<br /><br />In terms of physical properties, a planet=moon, and a planetoid=moonoid. The only distinction between the equating terms is whether it orbits a star or planet.<br />

 

[edawg]

i say we use our solar system for the template, lets break down surface conditions(alphabetic) into 1 category and planetary size into another(numeric),moons will retain their own category with the addition on surface conditions (Io,europa ect...?<br /><br />

 

[ghamoni]

I like the basis of the original draft proposal, based on minimum mass to make and object round however I am not happy that we would then get hundreds of objects all classified simply as planets. I would prefer to call these objects planets but to then classify them into major and minor planets. We would then end up with these objects:<br /><br />- major planets (the 8 largest planets) - the dominant planets in their orbits<br />- minor planets (all else including Pluto, Ceres, etc - Charon is up for debate)<br />- small solar system bodies (other non-planet, non-star objects) (possibly extended to small stellar system bodies for non-planets around other stars).<br /><br />This approach has the benefit that it is based on hard scientific rules to define a "planet" but also keeping the significant planets distinct. Textbooks would have to change 9 to 8 and replace references to "planet" with "major planet".

 

[harmonicaman]

<b>Ghamoni -</b><br /><br />Welcome aboard!<br /><br />I think you'll get your wish... It seems like they are now working on a proposal which will provide for only 8 "Major" planets and the rest will be "Planets" with a big <big><b>*</b></big> next to their names.<br /><br />I think this idea makes a lot more sense than just calling everything that's round a planet. Asteroids are Asteroids, KBOs are KBOs and Oort cloud objects are Oort cloud objects -- everything in its own little niche!<br /><br />This opinion is also shared by Dr. Michael Brown of Cal Tech; the discoverer Xena.