Astronomical distances
Solar system of Class 8
ASTRONOMICAL DISTANCES
The billions of stars and other heavenly bodies in the universe are separated by such a large distances, so the ordinary units for measuring distances on earth i.e. metres, kilometers or miles are not adequate for the purpose.
For measuring these extremely large distances, we use two astronomical units, the light year and the parsec.
A light year is defined as the distance travelled by light in one year.
The speed of light is 300,000 km/s and 1 year has 1 × 365 × 24 × 60 × 60 seconds.
∴ 1 Light year = 300000 × 365 × 24 × 60 × 60 km
1 Light year = 9.46 × 1012 km.
Another unit commonly used for measuring astronomical distances is the parsec.
1 parsec is equal to 3.26 light years.
The distance travelled bythe light at a speed of 300,000 km/s in one minute (60 seconds) is called a light minute.
1 light minute = × 1 minute = 18,000,000 km = 18 × 106 km.
