Why is the distance between stars expressed in light years? What do you understand by the statement that a star is eight light years away from the Earth?
Answer
The distance between the stars is so large that Kilometers becomes a very small unit.
Hence, the distance between stars and planets are expressed in light years .
One Light Year means Distance travelled by light in 1 Year.
Calculating 1 Light Year
Speed of Light = 3 × 10 8 m/s
Time = 1 Year
= 365 days
= 365 × 24 hours
= 31536000 seconds
Now,
1 Light Year = Speed × Time
= 3 × 10 8 × 31536000 m
= 94608000 × 10 8 m
= 94608000 × 10 8 × 1/000 km
= 94608 × 10 8 km
= 9.4608 × 10 4 × 10 8 km
= 9.4608 × 10 12 km
Now,
A star located 8 light years away means
Distance between star and earth = 8 light years
= 8 × 9.4608 × 10 12 km
= 8 × 9.4608 × 10 12 km
= 75.6874 × 10 12 km
= 7.56874 × 10 13 km
= 7.57 × 10 13 km
