Write a short note on the unit in which astronomical distances are measured.

The distances in universe are so large that ‘km’ becomes an extremely small unit to express such large distances. For example the various stars are millions of kilometers away, so ‘kilometer’ unit is not suitable to express the distances between the stars and other celestial objects. So the distances between various celestial bodies are expressed in the unit of ‘light year’. Light year is the distance light can travel in one year. We can calculate the value of ‘one light year’ in ‘kilometers’ by multiplying the speed of light (300000km/s) by the number of seconds in one year (31536000 s). One light year is equal to 9.46×10¹²kms.

Light year is not a unit of time but a unit of distance. If a star is 8 light years away from the earth, it mean that the distance of the star from the earth is so much that light from the star takes 8 years to reach the earth.