Solar System

• The solar system is the family of the sun, planets revolving around it, the satellites of the planets and the asteroids or meteoroids and comets etc.

• There are eight planets in the solar system.

• Starting from the sun there are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

• All the planets revolve around the sun in their orbits.

• Meteorite analysis shows that the age of solar system is about 4530 million years.

• The sun is not the largest star of the Milky Way; rather it is an average sized star.

• It is not at the centre of the galaxy but shifted towards a side.

• The diameter of the sun is 1, 392, 140 km and its mass is 2 * 1027 tonnes.

• The outermost layer of the sun is called photosphere, has an average temperature of 5570 0C.

• The photosphere rotates at a rate of 25.38 days per turn.

• At the centre of the sun hydrogen is undergoing nuclear fusion reaction which provides energy for the heat and light so sun.

• The planets of the solar system as well as the moons get light and sometimes heat from the sun.

• The four inner planets of the solar system are called terrestrial plants because of their rocky nature.

• The outer planets are called gaseous planets because they don’t have solid surface and are composed of gases.


1. Mercury

• Its distance from Sun is 58 million kms.
• Its revolution period is 88 days.
• Its rotation period is 58 days, 15 hours and 30 minutes.
• It has no moon.
• It is the nearest planet to the sun.
• It is also the smallest planet of the solar system.
• It is the fastest planet.
• Its radius is 2,433 kms and diameter is 4,878 kms.
• It is covered with holes called Craters.
• It has no atmosphere.
• The temperature on mercury vary between 420 0C (7900F) in the day and -180 0C (-2900F) at nights.

2. Venus

Apart from the moon, Venus is the brightest object in the sky. Venus can be seen with naked eye in the morning or in the evening. Following are the main characteristics of the Venus.

• Its distance from the Sun is 108 million kms.
• Its revolution period is 224.7/225 days.
• Its rotation period is 243 days and 14 hours (longest day)
• It has no moon.
• It is the nearest neighbour of the earth in the solar system.
• It is the brightest planet.
• It is also the hottest planet.
• Its diameter is 12,102 kms.
• It is wrapped in thick clouds of CO2 gas.
• It rotates from east to west as opposite to most other planets.

3. Earth

The earth is the largest and the densest of the four terrestrial planets. It is the most wonderful planet of the solar system. Following are the features of the Earth.

• Its distance from the Sun is 150 million kms.
• Its revolution period is 365 ¼ days.
• Its rotation period is 23 hours, 56 minutes, 40 seconds.
• It has one moon.
• It is the densest planet.
• It is also the watery and bios planet.
• Its diameter is 12756 km (7927 miles equatorial and 7900 miles polar diameter)
• It has atmosphere which contains 78% Nitrogen, and 21% Oxygen.
• Its two-thirds surface is covered with oceans.
• The earth’s surface is rich in Oxygen, Silicon, Aluminium, Iron, Calcium, Sodium etc.

4. Mars

• Distance form sun 228 million kms.
• Revolution period 687 days.
• Rotation period 24 h, 37 min and 22 sec.
• It has two moons Phobos and Deimos.
• Its diameter is 6794 kms.
• Mars is covered with red dust.
• It has an atmosphere composed almost entirely of CO2.
• Its average temperature is -53 0C.

5. Jupiter

• Its distance from sun is 778 million kms.
• Revolution period 12 years.
• Rotation period 9h, 50min, and 30 sec. (smallest day)
• It has 63 moons.
• It is the largest planet of the solar system.
• It has the largest number of satellites.
• Its diameter is 1, 24,800 kms.
• Its diameter is eleven times greater than the earth’s diameter.
• It has a dense, cloudy atmosphere of hydrogen and helium.
• It has a rock-iron-ice core about 15, 000 km (9,000 miles) thick.
• Jupiter radiates 67% more heat than it receives from the sun. this is mainly due to dissipation of the primordial heat of the planet.

6. Saturn

In 1610, Galileo became the first person to look at Saturn through telescope.

• Distance from Sun 1427 million kms.
• Revolution period 30 years.
• Rotation period 10h, 14 mins.
• It has 62 moons.
• The largest moon of Saturn is the Titan and it is the second-largest moon in the solar system. Titan is larger than the planet Mercury.
• It is the second largest planet.
• It has a magnificent system of rings.
• Its diameter is 1, 20, 000 km.

7. Uranus

When sky is very dark and very clear Uranus can be seen with the naked eyes. The planet was discovered by William Herschel in March 1787.

• Its distance from Sun is 2869.9 million kms.
• Revolution period is 84 years.
• Rotation period is 16h, and 10 mins.
• It has 27 moons.
• Titania is the largest moon of Uranus.
• It has an atmosphere which is dominated by hydrogen and helium.
• Its diameter is 52, 400 km.

8. Neptune

Neptune was discovered by the German astronomer Johann Galle.

• Distance from Sun 4496, 6 million kms.
• Revolution period 165 years (largest year)
• Rotation period 18 hours.
• Neptune has 13 moons that we know of. The largest moon is Triton.
• It is the coldest planet.
• It is the slowest to move around the sun.
• Its diameter is 49,100 kms.
• It is known as the twin of Uranus due to their similarity of size, mass and composition.