Why stars distances are measured in light years?

Answer 1

A light-year provides a readily convertible distance that is large enough that vast stellar distances can be expressed in smaller, easily compared numbers. For example, distances to "nearby" stars are from 4 to about 25 light-years, while a galaxy's diameter may be 100,000 light-years or more, and the distances between galaxies are in the millions and billions of light-years.

Using kilometers would require larger named numbers or exponents, which could be less clear. Each light-year is about 1.2 trillion kilometers or about 978 billion miles.

For shorter distances, a useful unit is the AU, or Astronomical Unit. This is the average distance between the Earth and the Sun, about 93 million miles. If we were measuring or comparing the distances of planets from the sun, they would be expressed in AU's and not light-years. For further distances the light-year is used. It is easier to say 4.2 light-years to Proxima Centauri than 4,125,987,200,000 miles.

Another even larger unit, the parsec (parallax second), is based on astronomical angular measurement and is equal to about 3.26 light-years.

Answer 2

Good question, by the way. The light year is at the moment a singular longest distance measurement that we use. Approximately 977.616 billion miles. The other term we use for distance is the AU, or Astronomical Unit. This is the equivalent of the distance between the earth and the sun, or 93 million miles. If we were measusing or comparing the distances of planets from the sun, they would be measured in AU's and not light years. For further distances the light year is used. Its easier to say 4.2 light years to Alpha Proxima than 4,125,987,200,000 miles. Who knows. When we start measuring things that are thousands or millions of trillions miles apart, we might come up with another term for long distance measurement. It might even be you who gets to name it.

Answer 3

A light-year provides a readily convertible distance that is large enough that vast stellar distances can be expressed in smaller, easily compared numbers. For example, distances to "nearby" stars are from 4 to about 25 light-years, while a galaxy's diameter may be 100,000 light-years or more, and the distances between galaxies are in the millions and billions of light-years.

Using kilometers would require larger named numbers or exponents, which could be less clear. Each light-year is about 1.2 trillion kilometers or about 978 billion miles.

For shorter distances, a useful unit is the AU, or Astronomical Unit. This is the average distance between the Earth and the Sun, about 93 million miles. If we were measuring or comparing the distances of planets from the sun, they would be expressed in AU's and not light-years. For further distances the light-year is used. It is easier to say 4.2 light-years to Proxima Centauri than 4,125,987,200,000 miles.

Another even larger unit, the parsec (parallax second), is based on astronomical angular measurement and is equal to about 3.26 light-years.

Answer 4

Because of the huge distances involved. A light year is a term of measurement rather than time - i.e. the distance light can travel in one year. Light travels at 299 792 458 metres per second, so the distance in one light year is huge (299792458 x 60x 60 x 24 x 365 = 9400000000000000). is easier to say a star is, say, 100 light years away than saying it is 940000000000000000 metres way (940 million billion metres way.

Answer 5

It has become customary to use light-years, or parsec, instead of meters, probably because it's easier to work with the small numbers that result when using light-years.