Planets and the Solar System

Before 2006 we recognize there are 9 planets in our solar system including Pluto. But after the 2006 meeting of the IAU's General Assembly, the astronomers exclude Pluto from the Planets. The number of planets are 8 now. And Pluto become a dwarf planet along with others such as Makemake and Eris.

above: Mars and Mercury
below: the Moon, dwarf planets Pluto and Haumea

Below is the Enlarged pictures of the lowest object in the above picture.

above: Mars and Mercury
below: the Moon, dwarf planets Pluto and Haumea

According to the IAU, there are eight planets and five recognized dwarf planets in the Solar System. In increasing distance from the Sun, the planets are:

☿ Mercury

♀ Venus

⊕ Earth

♂ Mars

♃ Jupiter

♄ Saturn

♅ Uranus

♆ Neptune

Jupiter is the largest, at 318 Earth masses, whereas Mercury is the smallest, at 0.055 Earth masses.

The planets of the Solar System can be divided into categories based on their composition:

The inner planets. From left to right: Mercury, Venus, Earth and Mars

Terrestrials: Planets that are similar to Earth, with bodies largely composed of rock: Mercury, Venus, Earth and Mars. At 0.055 Earth masses, Mercury is the smallest terrestrial planet (and smallest planet) in the Solar System, whereas Earth is the largest terrestrial planet.

The four gas giants against the Sun: Jupiter, Saturn, Uranus, Neptune

Gas giants (Jovians): Planets largely composed of gaseous material and significantly more massive than terrestrials: Jupiter, Saturn, Uranus, Neptune. Jupiter, at 318 Earth masses, is the largest planet in the Solar System, whereas Saturn is one third as big, at 95 Earth masses.

You cannot land a plane or anything in these Gas Giant Planets since they are made of gas.

Ice giants, comprising Uranus and Neptune, are a sub-class of gas giants, distinguished from gas giants by their significantly lower mass (only 14 and 17 Earth masses), and by depletion in hydrogen and helium in their atmospheres together with a significantly higher proportion of rock and ice.

Dwarf planets: Before the August 2006 decision, several objects were proposed by astronomers, including at one stage by the IAU, as planets. However in 2006 several of these objects were reclassified as dwarf planets, objects distinct from planets. Currently five dwarf planets in the Solar System are recognized by the IAU: Ceres, Pluto, Haumea, Makemake and Eris. Several other objects in both the asteroid belt and the Kuiper belt are under consideration, with as many as 50 that could eventually qualify. There may be as many as 200 that could be discovered once the Kuiper belt has been fully explored. Dwarf planets share many of the same characteristics as planets, although notable differences remain – namely that they are not dominant in their orbits. By definition, all dwarf planets are members of larger populations. Ceres is the largest body in the asteroid belt, whereas Pluto, Haumea, and Makemake are members of the Kuiper belt and Eris is a member of the scattered disc. Scientists such as Mike Brown believe that there are probably over one hundred trans-Neptunian objects that qualify as dwarf planets under the IAU's recent definition.

Type	Name	Equatorial Diameter	Mass	Orbital period (years)	Rotation period (days)	Confirmed Moons	Rings
Terrestrial	Mercury	0.382	0.06	0.24	58.64	0	no
	Venus	0.949	0.82	0.62	243.02	0	no
	Earth	1	1	1	1	1	no
	Mars	0.532	0.11	1.88	1.03	2	no
Gas giant	Jupiter	11.209	317.8	11.86	0.41	67	yes
	Saturn	9.449	95.2	29.46	0.43	62	yes
	Uranus	4.007	14.6	84.01	0.72	27	yes
	Neptune	3.883	17.2	164.8	0.67	14	yes
Dwarf planet	Ceres	0.08	0.0002	4.6	0.38	0	no
	Pluto	0.18	0.0022	248.09	6.39	5	no
	Haumea	0.15×0.12×0.08	0.0007	282.76	0.16	2	?
	Makemake	0.12	0.0007	309.88	0.32	0	?
	Eris	0.19	0.0025	557	0.3	1	?

Reference:

http://solarsystem.nasa.gov/planets/

http://en.wikipedia.org/wiki/Planet