Facts About Our Solar System

Our solar system is made of eight planets, moons, asteroids and also of thousands of meteoroids  It is said that it was formed about 4.6 billions years ago. Astronomers say that each and every physical body and energy that exist at present time had been once highly concentrated form at one point, and scientists believe after a Big Bang, our Universe, stars and solar system were formed.
There are only 8 planets in our solar system and Pluto has been recently eliminated from the list since it's being a dwarf planet.

Sun is lying at the quite center place of this solar system and it comprises more than 99.5% of total mass of solar system. It is mostly made up of (98.5%) Hydrogen and Helium gases and remaining 1.5% is composed of Oxygen, Nitrogen  Neon, Carbon, Silicon, Iron, Magnesium and Sulfur. Due to the gravitational force exerted by the sun, all the eight planets revolving around it in their own orbits. Sun has a great diameter of 1.39*10^6 Km and if it were a hallow ball, more than 13 lacs of earths would be required to fill in it.

Properties Of Terrestrial Planets

Planet	Distance From The Sun in Km	Radius in Km	Mass in Kg	Mean Density in gm/cc	Rotation Period	Orbital Period
Mercury	5*10^7	2,439	3.30*10^23	5.4	176 days	88 days
Venus	10.8*10^7	6,052	4.86*10^24	5.2	243 days	225 days
Earth	14*10^7	6,371	5.97*10^24	5.5	24 hrs	365 days
Mars	22.7*10^7	3,396	6.4*10^23	3.39	25 days	686 days

Among the eight planets Mercury, Venus, Earth and Mars are known as inner or terrestrial planets. All these four planets are smaller in size and mainly made up of rocks, soil, iron core metals and minerals. All of them have iron core and their mean density is higher than that of giant outer planets. Except our earth no one has moon. They take more time to complete one rotation than outer planets, however,their revolution speed is higher than outer planets have.

Properties Of Outer Planets

Planet	Distance From The Sun in Km	Radius in Km	Mass in Kg	Mean Density in gm/cc	Rotation Period	Orbital Period	Number Of Moons
Jupiter	77.8*10^7	66,854	1.898*10^27	1.32	10 hrs	11.86 years	63
Saturn	140*10^7	60,268	5.7*10^26	0.687	10.5 hrs	29.5 years	61
Uranus	300*10^7	25000	8.7*10^25	1.27	17.5 hrs	84 years	27
Neptune	455*10^7	24,340	1.02*10^26	1.64	16 hrs	165 years	13

Jupiter, Saturn, Uranus and Neptune are four outer planets of the solar system. These planets are mostly composed of gases like Hydrogen, Helium, Nitrogen, Methane and Ammonia. Since they are lying far away from the sun, the temperature will be very low in their surface atmosphere. However, the temperature will steadily increase towards the core of these planets due to extreme pressure of gases. They spin faster than terrestrial ones,but, revolve slowly in their orbits.The outer planets contain relatively small rocky core surrounded by metallic Hydrogen and Helium.