EVERYDAY SCIENCE

Detailed explanation-1: -Stars are away from the earth millions of kilometres away. It is not convenient to express such a large distance in the units of km. So, the distance of stars from the earth is expressed in light years. One light year is the distance that light travels in one year in a vacuum.

Detailed explanation-2: -The Parallax Angle–How Astronomers Use Angular Measurement to Compute Distances in Space. The parallax angle is the angle between the Earth at one time of year, and the Earth six months later, as measured from a nearby star. Astronomers use this angle to find the distance from the Earth to that star.

Detailed explanation-3: -Hence, the large distances are expressed in light-years. If a star is located 8 light-years away from the earth, it means that the distance between the star and the earth is the distance light would travel in eight years. So, the distance between the earth and star = 8 ✕ (9.46 ✕ 1012) = 7.6 ✕ 1013 km.

Detailed explanation-4: -The main reason for using light years, however, is because the distances we deal with in space are immense. If we stick to miles or kilometers we quickly run into unwieldy numbers just measuring the distance to the nearest star: a dim red dwarf called Proxima Centauri that sits a mere 24, 000, 000, 000, 000 miles away!

Detailed explanation-5: -For the same reason, astronomers don’t use miles to measure vast distances in space. Instead, they use light-years: the distance that light travels in a year. That makes Proxima Centauri, the closest known star to the Sun, 4.28 light-years away; that’s a lot easier than saying 24, 000, 000, 000, 000, 000 miles.