Question

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? [3 marks]

Answer 1

1. The distance of the stars from the Earth and the distance between the stars are very large. It is inconvenient to express these distances in kilometer (km). (1 mark)

2. Thus, these large distances are expressed in light years. One light year is the distance travelled by light in one year. One light year is equal to $9.46\times {10}^{12}km$. (1 mark)

3. A star is located eight light years away from the Earth. This means that the distance between the star and the Earth is equivalent to the distance travelled by light in eight years, i.e., a star is located $8\times (9.46\times {10}^{12})=7.6\times {10}^{13}km$ away from the Earth. (1 mark)