2007-01-11 12:02:24 · 6 answers · asked by harleydavidson218 2 in Science & Mathematics ➔ Astronomy & Space
There is no set scientific definition for planet (from the Greek planetes “wanderers”), but as a rule of thumb, a planet: 1) must directly orbit a star or an object that has nuclear fusion; 2) must be small enough that it has not undergone internal nuclear fusion (ie, it is not a star or starlike object); and 3) must be large enough that its self-gravity gives it the general shape of a sphere.
2007-01-18 09:24:44 · answer #1 · answered by anecentric 2 · 0⤊ 0⤋
If I remember the IAU resolution correctly, there are three basic criteria for the classification of "planet" --
1. Is in orbit around a star.
2. Is massive enough that self-gravity causes the body to be more or less spherical in shape.
3. Is the most significant body in the general neighborhood of its orbit.
The third definition is the one that gets a lot of people upset. There is a Wikipedia article talking about this (can't remember the reference at the moment). Apparently, there is a parameter that can be calculated to determine whether a given body is the most significant one in its neighborhood. A table accompanying the article lists this parameter's value for the eight defined planets as well as the three/four defined dwarf planets. There is a massive difference between the two groups in terms of this parameter.
BTW, there is still a question as to whether Charon should be a moon or a dwarf planet. I think the resolution also addressed by saying if the center of gravity of the two bodies in question is in the space between the bodies, the system should be considered a double planet. If this is the case, then Pluto/Charon is a double planet and Earth/Moon is not.
2007-01-11 20:17:09 · answer #2 · answered by eriurana 3 · 0⤊ 0⤋
Basics for our solar system:
Terrestrial (Inner):
Size: Smaller.
Composition: Solid.
Temperature: Hot.
Spacing: Closest to the sun.
Jovian (Outer):
Size: Bigger.
Composition: Gaseous with only a solid core.
Temperature: Cold.
Spacing: Farthest from the sun.
2007-01-11 20:22:30 · answer #3 · answered by mosquitoe_13 3 · 0⤊ 0⤋
Round or oval(for the most part), spinning and orbiting around a central star or binary star.
2007-01-17 13:00:52 · answer #4 · answered by au197_0 3 · 0⤊ 0⤋
1) Is spherical
2) Orbits the Sun
3) Clears its surroundings of large debris
2007-01-11 20:05:41 · answer #5 · answered by CircleSeven 2 · 1⤊ 0⤋
weather it is jovian or terrestrial...
2007-01-11 20:09:08 · answer #6 · answered by wind it up 4 · 0⤊ 0⤋