How are distances in space calculated?

They often use the light from a Cepheid Variable star. They also use Parallax and the light from supernovas to estimate distance.

http://universe-review.ca/R02-07-candle.htm

Hi. Space and Time are like two sides of the coin. Space is measured in terms of time. In other words by the speed of light. It could be light years or even light hours, i.e. the time taken by light to travel a given distance. The speed of light is constant 1,86,000 miles per second. The nearest star is some four light years away. It takes 8 minutes for the sunlight to reach the earth. Is it clear now?

First, they can always be calculated in kilometers.

But, for distances from the sun (for solar system objects), the Astronomical Unit is used. 1 AU is the distance from Earth to the Sun. This is a useful way of measuring in the solar system because the numbers stay low and it gives a sense of proportion. For example Pluto is somewhere around 39 AUs away from the Sun. Better than 35 million kilometers (not actual number), which is nearly meaningless (and harder to do math with) to us. Distances from planets to their moons are not calculated in this way for the same reason: .00001 AU means little.

For interstellar distances, the light year is used, it is the measure of distance that a light wave/particle travels in one year. The closest star, Alpha Centauri, is about 4.5 light years away or about 27 trillion kilometers - the LY is easier. Since the galaxy is about 100,000 light years wide, the numbers stay relatively small.

We dont use AUs for interstellar because it would create the problem of large numbers again - a light year would be around 600,000 AUs. But light-minutes or hours could be useful to measure within the solar system (it takes 8 light minutes to get to the sun from earth), but it is not widespread.

The distances to stars are calculated using something called the parallax of the star, or it's apparent motion in the sky over the course of year. Take a look at this wiki article, it has some great pictures, hope this helps!

A unit of interstellar distance, defined as the distance light travels in a period of one year. The speed of light is constant, at about 300,000 km per second: a light year is very nearly 10 million million km. From an Earthbound perspective, this is a vast distance - our entire Solar System, out to the orbit of Pluto, is only one eight-hundredth of a light year across.

in light year

1 light year= the distance light can go in a year

=365*24*60*60*3 x 10^8 meter

Light years,ie:- the time it take for a 60W light globe to burnout.

It is caculated in LIGHT YEAR.

1Light year = 9.46*10^12 kms.

light years and amstrong units

lightyears, which is how far light can travel in one year.