Universe And Solar System (World Geography) (Part-2)

Proxima Centauri, the closest star to our solar system, is still 40,208,000,000,000 km away. (Or about 268,770 AU.) When we talk about the distances to the stars, we no longer use the AU, or Astronomical Unit, commonly, the light year is used.

A light year is a unit of distance, not time. It represents the distance that light travels in one year in a vacuum. Key Facts about a Light Year:

• Speed of light = approximately 299,792 kilometers per second (or about 186,000 miles per second).
• In one year, light travels about:

9.46 trillion kilometers
or 5.88 trillion miles 

• The nearest star to Earth (after the Sun) is Proxima Centauri, which is about 4.24 light years away.

Proxima Centauri, the closest star to our solar system, is still 40,208,000,000,000 km away. (Or about 268,770 AU.) When we talk about the distances to the stars, we no longer use the AU, or Astronomical Unit, commonly, the light year is used.

A light year is a unit of distance, not time. It represents the distance that light travels in one year in a vacuum.

Key Facts about a Light Year:

• Speed of light = approximately 299,792 kilometers per second (or about 186,000 miles per second).
• In one year, light travels about:

9.46 trillion kilometers
or 5.88 trillion miles

• The nearest star to Earth (after the Sun) is Proxima Centauri, which is about 4.24 light years away.

Jupiter, Saturn, Uranus and Neptune are the outer planets of the Solar System. While Mercury, Venus, Earth and Mars are the inner planets. The main asteroid belt is located in the orbits of Jupiter and Mars.

8 Planets in Order:

1. Mercury – Smallest, closest to the Sun.
2. Venus – Hottest planet, thick atmosphere.
3. Earth – Our home, supports life.
4. Mars – The Red Planet.
5. Jupiter – Largest planet, gas giant.
6. Saturn – Known for its beautiful rings.
7. Uranus – Rotates on its side, icy giant.
8. Neptune – Farthest, cold and windy.

The bright part of the Sun is called the photosphere. The corona is visible in the event of a total solar eclipse.

Sunlight takes 8 minutes and 16.6 seconds (approximately) to reach Earth. The average distance between the Earth and the Sun is about 140 million, 96 lakh km.

Explanation:

• Distance from Sun to Earth = about 149.6 million kilometers
• Speed of light = 299,792 kilometers per second
• Time = Distance ÷ Speed = 149.6 million km ÷ 299,792 km/s ≈ 500 seconds
• 500 seconds = 8 minutes and 20 seconds

The point of the orbit of various bodies revolving around the Sun, such as planets and comets, etc., which is located at the most distance from the Sun, is called Aphelion.

Aphelion and Perihelion –

These terms describe the Earth’s varying distance from the Sun during its elliptical orbit.

The earth rotates around its axis from west to cast, The Earth makes one revolution on its axis in about 24 hours.

Key Points:

• This is called counterclockwise rotation when viewed from above the North Pole.
• Because of this:

The Sun rises in the east and sets in the west.
All planets in the Solar System (except Venus and Uranus) also rotate in this direction.

Pluto was removed from the category of planets and put in the category of the dwarf planet (Dwarf). So at present, the number of planets is 8.

After August 2006, Pluto was removed from the category of planets and put in the category of the dwarf planet (Dwarf).

Dwarf Planets –

A dwarf planet is a type of celestial body in space that shares some features with regular planets but does not meet all the criteria to be called a full planet.

Definition (as per IAU – International Astronomical Union):

A dwarf planet:

1. Orbits the Sun
2. Has enough mass to be almost round in shape
3. Has not cleared its orbit of other debris
4. Is not a moon of another planet