Planetary Classification System

[cy_el]

Since everyone already knows about the basics of the argument of sorts, on one side or the other, as to the definition of objects orbiting the star of our solar system, I'll bypass explaining it. To those who for some reason aren't aware of it, explanation can be found here:<br />http://www.space.com/scienceastronomy/050802_planet_definition.html<br /><br />The reason I write this...is because I believe I've come up with a working theory/solution that might satisfy the more rational members of the public as well as scientific community.<br /><br />To summarize:<br />A planet would be the classification of an astronomical body orbiting a star that has been verified to contain sufficient mass to have a spherical form due to self gravity, but not sufficient to cause thermonuclear fusion to begin within it. Both stars, asteroids and comets are thus all separated in definition, as well as objects that may be large enough to be planets themselves but are gravitationally in orbit around another, not the star itself.<br />Planets as they are known in our solar system thus far would come to be identified under one of two scientific categories (perhaps to be thought of as "kingdoms"), those of the "classical" solar-plane (SP) planets, the most recent of which was discovered in 1846, and non-solar-plane (NSP) planets, the most recent of which was discovered, as of this writing, this year. The differentiation is thus a truly scientific one, while keeping the public-opinionated notion of "planet" present: while both "kingdoms" obey the conform to the requirements first given above, an SP-planet orbits on the solar ecliptic, whereas an NSP- does not. Pluto would not then be "demoted" by calling it a non-solar-plane, except only in the minds of the deliberately obtuse; its self-descriptive NSP- status would merely be reality...the ways things are. Ceres, in fact, might well be one to rec

 

[Philotas]

<blockquote><font class="small">In reply to:</font><hr /><p>Ceres, in fact, might well be one to receive substantial change, and be upgraded to NSP- classification, if its gravity pulls its mass together into a sphere as photos have indicated.<p><hr /></p></p></blockquote><br /><br />Surely, you mean upgraded to SP? <br />An upgrade of Ceres is what alot of people "fear", so it depends how they would react. <br />Also, wouldn`t it be arbitrary how much a planet could be inclined to the ecliptic before it would become an NSP? It might also be bit unfair for any />Mars sized object that might be lurking in the KB or Oort Cloud to be defined as 'lesser' planets. I agree that having at least two different definitons for planets is the way to go, but think size or history should have something to say rather than inclination. I mostly agree as long as all round objects in this solar system orbiting the Sun are called planets. <div class="Discussion_UserSignature"> </div>

 

[vogon13]

And if you include objects orbiting planets (of any stripe) or each other, or congregating in groups (like Jupiters' 2 clusters of Trojans), etc., we can get into an interesting field of nomenclature.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[cy_el]

According to data I looked up on Ceres, it is inclined 10 degrees off the ecliptic...90 degrees would make it a polar orbit, which is basically the "furthest" NSP possible, no? Likewise, isn't the orbit of Ceres not fully ovoid in its revolution, i.e. in the same manner that Pluto is moving into winter (or supposed to be) by means of distance from the sun, but the classic planets' seasons are based on their axial-tilt? Indeed (and many thanks for the idea here)...another requirement that can be added, for the tilt of rotation of an astronomical body to determine any extant seasonal change, if it were SP?<br /><br />In a way, it would be arbitrary, the number of degrees used...in another way it wouldn't, if our planet was used as astronomical zero latitude of sorts, since AUs is already a measure of distance based solely on our planet's distance from Sol, and the metric system is likewise based on measurements of Earth itself.<br /><br />Next concept, then: To identify the furthest distance possible before the planet is considered to be offset from the ecliptic, simply judge what is the largest number of degrees any of the other "classic" worlds have, and allow for only a given percentage of further degrees before it changes. If one goes as high as 100% extra...then here my supposition may be off, but wouldn't that not be very far, since the eight classics are indeed basically on the same plane? Forgive if this is highly uneductated and I haven't checked recently, but isn't something on the order of a single degree the most in terms of change between a given Earth and a given (insert; Neptune for instance)? If it weren't, why would a million solar system maps show them neatly on a flat plane?

 

[Philotas]

Ok, here`s an overview of the planets inclinations` to the ecliptic:<br /><br />Mercury : 7.004 87°<br />Venus : 3.394 71°<br />Earth : 0.000 05°<br />Mars : 1.850 61°<br />Jupiter : 1.305 30°<br />Saturn : 2.484 46°<br />Uranus : 0.769 86°<br />Neptune : 1.769 17°<br />Pluto : 17.141 75°<br /><br />As you see, Pluto is totally different from the other planets. Mercury, however, almost have the same inclination as Ceres and have 7° higher inclination than the the planet with the lowest inclination, Earth. Also Venus is on the edge. So you have to put the 'circular orbit defintion' in too, otherwise you want to exclude Mercury from it`s planethood. <div class="Discussion_UserSignature"> </div>

 

[cy_el]

9 degrees. Anything inside 10% towards polar orbit is SP. Anything beyond that is NSP.<br />10%, somewhat arbitrarily likewise, would be the measure by which a planet could be off a sun-centered orbit. If the sun is 10% of the diameter of a planet's orbit or nearer away from the hypocenter of the orbit, it could be SP (if the orbital inclination is likewise aligned). Outside that would be the alternative.<br /><br />To some the first definition might sound 'cute', since Ceres is just one degree off, but I for one "ould promise to hold to it," if some once-in-a-lifetime astronomical event altered Ceres to 7 degrees, for instance, and its orbit to a more circularly-balanced one ( then I would support Ceres being newly introduced as a rocky planet, in the classic sense, in the outer solar system.<br /><br />Then again, when you look up 1 Ceres on online encyclopedias, it is called an asteroid...its gravity giving it, to quote: "...a nearly spherical shape, much like a planet." (www.wikipedia.com, 1 Ceres) Well, is it or isn't it? If it is held together by atomic forces, and not made spherical by its own gravity, it's an asteroid, and if the reverse, only then a planet, no?

 

[Philotas]

http://upload.wikimedia.org/wikipedia/en/c/c0/1_ceres_hst_2005.jpg<br /><br />Well, as this image suggest, Ceres is spherical in shape. Although one might wait before concluding something like that until the Dawn spacecraft arrives in 2015, or the James Webb Telescope can take a better image somewhat earlier.<br /><br />For comparisasion Enceladus is 505km in diameter and clearly spherical, while is Ceres almost twice as big. <div class="Discussion_UserSignature"> </div>