Chapter 8 : Planets of the Solar System
The Sun is by far the largest object in the solar system.
It contains more than 99.8% of the total mass of the Solar System (Jupiter contains most of the rest).
The Sun is a star at the center of the solar system.
Without the Sun, Earth could not support life.
The Sun gives off heat and light that the Earth needs to support life.
Topics covered in this snack-sized chapter:
Approximate age: 4.6 billion years.
Approximate core temperature: 15,000,0000
It is about 4.6 billion years old and will continue to shine as it does now for about 5 billion more years.
Mercury is the smallest and closest to the Sun of the eight planets in the Solar System.
Length of year (in Earth days): 88 earth days.
Distance from Sun (million km): 45.9 to 69.7
Number of rings: 0
Number of known moons: 0
Venus is the second planet from the Sun.
It is the hottest planet due to the high amount of carbon dioxide in its atmosphere; this causes the greenhouse effect.
The high temperature, enormous atmospheric pressure (90 times that of Earth) and its sulphuric acid clouds makes the environment extremely hostile to life.
The Earth is the third planet from the Sun and also the one where life exists.
It is the largest and densest rocky planet and the only one known to support life.
The Earth’s atmosphere protects it from the Sun’s harmful radiations and meteorites, trapping enough heat to support life.
About 70% of Earth is covered by water.
The Earth has one moon which is large enough for both bodies to be considered as a double planet system.
- 1% Water vapor, argon, carbon dioxide and other trace gases
The red planet; Mars is the fourth planet from the Sun and the outermost rocky planet.
When astronomers first observed the surface of Mars they observed canals and vegetation which were thought to be signs of life on Mars.
Now these ‘canals’ are optical illusions and the ‘vegetation’ is dark patches where the red dust on the surface has been blown away.
The solar system’s largest volcano exists on Mars; the 600 km wide and 25 km high Olympus Mons.
The Martian atmosphere is much thinner than Earth’s atmosphere with only a few clouds and morning mists.
- 0.7% Oxygen, carbon monoxide and water vapor.
The first of the four gas giants.
Jupiter is the fifth planet from the sun and is the largest planet in the solar system.
Rings of Jupiter: Jupiter has a faint planetary ring system composed of three main segments:
- An inner torus of particles known as the halo.
- A relatively bright main ring, and
Number of known moons: 63
- These rings appear to be made of dust, rather than ice as with Saturn's rings.
It has a diameter 11 times greater than the Earth.
It has mass 2.5 times than the combined mass of the eight other planets.
One of Jupiter’s moons called Europa is 3,138 km in diameter, covered in ice.
- 10% Helium with traces of ammonia, methane and water vapor.
- Scientists say that under the ice layer there may be water, which may then support life.
The Planet Saturn is the second largest planet.
It is the next planet after Jupiter.
Saturn is named after a Roman God and is famous for its beautiful rings.
Saturn's rings are made of billions of ice particles.
Its surface consists of liquid and gas.
Saturn is the least dense of the planets; its specific gravity (0.7) is less than that of water.
Saturn is the sixth planet from the Sun.
- 6% Helium with traces of ammonia, methane and water vapor.
Uranus is the seventh planet from the Sun and also the third largest.
The atmosphere contains traces of methane which gives the planet a blue-green color.
- Though the planet is quite featureless with only a few methane clouds being spotted so far in the atmosphere.
Neptune is the eighth and farthest planet from the Sun in the Solar System.
Neptune is a gas planet with four rings and eight moons.
Like Jupiter, it also contains large cloud storms called the Great Dark spot (as wide as the Earth) and the Small Dark spot, which are pushed around the planet by winds of about 2000 kilometres per hour.
It is true that Pluto is no longer a planet, but it is categorized under the dwarf planet.
A dwarf planet is a planetary-mass object that is neither a planet nor a satellite.
For an object to be called a planet, it needs to meet certain characteristic features:
- This is because; Pluto fails to meet the specific requirements of being a planet.
- It should be large enough and have sufficient center of gravity to become spherical.
- It should be a dominating body in its orbit.