Show Planets | Show Major Moons | Show Minor Moons | Just Solar System | Show All     Database: (11 planets) (19 moons) (210 exoplanets)
Name ↑ ↓	Distance Sun (AU) ↑ ↓	Orbital Radius (km) ↑ ↓	Periapsis (km) ↑ ↓	Apoapsis (km) ↑ ↓	Period ↑ ↓	Mean Velocity (m/s) ↑ ↓	Eccentricity ↑ ↓	Inclination ↑ ↓
Mercury	0.38 AU	57,350,000	45,000,000	69,700,000	88.0d	47870	0.2060	7.00°
Venus	0.72 AU	108,200,000	107,400,000	109,000,000	224.7d	35020	0.0070	3.39°
Earth	1.00 AU	149,500,000	147,000,000	152,000,000	1y 0.0d	29783	0.0170	0.00°
Mars	1.52 AU	227,500,000	206,000,000	249,000,000	1y 321.8d	24100	0.0930	1.85°
1 Ceres	2.77 AU	413,715,000	380,612,000	446,818,000	4y 217.8d	17882	0.0800	10.00°
Jupiter	5.20 AU	778,300,000	740,900,000	815,700,000	11y 315.8d	13060	0.0480	1.30°
Saturn	9.54 AU	1,427,000,000	1,347,000,000	1,507,000,000	29y 159.2d	9600	0.0560	2.49°
Uranus	19.19 AU	2,870,694,703	2,735,000,000	3,006,389,405	84y 30.7d	6800	0.0470	0.77°
Neptune	30.06 AU	4,496,500,000	4,456,000,000	4,537,000,000	164y 330.6d	5430	0.0090	1.77°
134340 Pluto	39.48 AU	5,905,500,000	4,436,000,000	7,375,000,000	248y 43.7d	4740	0.2480	10.00°
136199 Eris	67.68 AU	10,125,000,000	5,650,000,000	14,600,000,000	557y 83.6d	3436	0.4420	10.00°
		Definition of a Planet: On August 24th, 2006 the International Astronomical Union (IAU) declared the official definition of a planet: RESOLUTION 5A The IAU therefore resolves that "planets" and other bodies in our Solar System, except satellites, be defined into three distinct categories in the following way: (1) A "planet"1 is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit. (2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape2 , (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite. (3) All other objects except satellites orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies". Opinion: The word planet is derived from the ancient Greek planetai which meant 'wanderer' and refered to any visible object in the heavens except the fixed stars. This meant that the Sun and Moon were considered planets but not the Earth. Throughout history several bodies have joined the ranks of planets and others have been dropped. Jupiter's four large moons and those of Saturn were considered planets at different points. Ceres, the largest asteroid, was considered a planet for several years until it was realized that it was just one among a multitude of other bodies with similar orbits. Today Ceres is once again a planet, albeit a dwarf planet. The point is that the term planet has always been a vague concept at best. It is silly that a prestigious scientific organization has decided to give an official definition to such a term. Arguments for and against planethood is more of a philosophical debate than a scientific one. The truth is worlds, planets, moons, celestial bodies, or whatever you call them doesn't change what they really are, facinating and wonderful.
Saint Petersburg Astronomy Club | The Mirror Lab
images Courtesy NASA/JPL-Caltech.