## Solar System

 12.1 Solar System

Comparison of Planet Distances in the Solary System from the Sun

1 ) Astronomical Unit (A.U.)

 $$1 A.U. = 1.5 \times 10^8 \text{ km}$$
• To convert  units between astronomical unit and km:
 Distance in A.U $$=\dfrac{ \text{Distance in km}}{1.5 \times 10^8\text{ km}}$$

2 ) Light Years (ly)

 1 light year $$= 9.5 \times 10^{12}\text{ km}$$
• To convert units between light years and km :
 Distance in ly $$=\dfrac{\text{Jarak dalam km} }{9.5 \times 10^{12}\text{ km}}$$

Planets in the Solar System

1. Mercury - the closest planet to the Sun
2. Venus -  the second closest planet to the Sun
3. Earth - the third planet from the Sun
4. Mars - the fourth planet from the Sun
5. Jupiter - the fifth planet from the Sun
6. Saturn - the sixth planet from the Sun
7. Uranus - the seventh planet from the Sun
8. Neptune - the eighth planet from the Sun

Characteristics of Planets

 Relationship between Temperature of a Planet and the Sun Thoretically, planets that are closer to the Sun would receive more heat. However, the situation in reality is rather complex. The surface temperature (°C) for each planet is :  Mercury - (-173°C to 427°C) Venus - (462°C) Earth - (-89.2°C to 56.7°C) Mars - (-143°C to 35°C) Jupiter - (-108°C) Saturn - (-139°C) Uranus - (-197.2°C) Neptune - (-201°C)
 Relationship between Density and Gravitational Pull of the Planets The gravity on the surface of a planet depends on its mass and density The gravity of Mercury and Mars is lower than Earth as their masses are lower than Earth The gravity of Venus is almost same as Earth, as their mass is almost same The gravity of Jupiter is much higher than Earth as the mass is extremely high Saturn, Uranus and Neptune have high mass, but the gravity is not as high as Earth because these 'giant gas' planets have low density
 Relationship between Distance, Time and Speed The further a planet is from the Sun, the more time it needs to orbit the Sun
 Rotational direction of the planets They rotate from west to east except Venus and Uranus Venus rotates from east to west  Uranus rotates on its side

Hypothetical Situation related to the Solar System

 What happens if the rotation of the Earth slos down or stops completely? Change in high and low tides Longer day and night duration in two different parts of the Earth More desert areas in parts of the Earth that faces the Sun Temperature will drop in areas of the Earth that do not receive sunlight

The Earth as a Planet for Living Things

 Characteristics of the Earth
• Has a lot of water
• Has high oxygen content
• Has a suitable temperature range
• Its atmosphere blocks harmful ultraviolet rays from reaching the Earth