Why do astronomers use light years to measure distances in space?

Answer 1

There has to be something standardized to use to measure such vast distances.
The distance that a beam of light travels in one year is pretty standard, so why not?

Answer 2

It is not correct that the Astronomical Unit (AU) has in any way superseded the Light Year. The AU is the mean distance between the earth and the sun, or 93,000,000 miles, which is a handy measure for such distances as planetary orbits and the orbits of moons.

For distances involved in reasonably nearby stellar objects, the light year is a suitable measure, being about 5.88 trillion miles.

There are units suitable for much greater distances in space. The most common is the Parsec, which means distance to a theoretical object that shows a parallax of one second of arc as the earth revolves once around the sun.

You can look up "parsec" or just take it as 3.086x10^16 miles, or about 3.262 light years. Astronomers also speak of "kiloparsecs," which means thousands of parsecs, and "megaparsecs," which means millions of parsecs.

Answer 3

They don't any more they use the term Astronomical Unit or AU to denote distance in space
A light-year or lightyear (symbol: ly) is a unit of measurement of length, specifically the distance that light travels in a vacuum in one year. While there is no authoritative decision on which year is used, the International Astronomical Union (IAU) recommends the Julian year.

A light-year is equal to:

9,460,730,472,580.8 km (about 9.461 Pm)
5,878,625,373,183.61 statute miles
about 63,240 astronomical units
about 0.3066 parsecs
The exact length of the light-year depends on the length of the reference year used in the calculation, and there is no wide consensus on the reference to be used. The figures above are based on a reference year of exactly 365.25 days (each of exactly 86,400 SI seconds). This is the value recommended by the IAU. However, other reference years are often used (e.g. Yahoo's and Google's calculators use a smaller value than the IAU), thus the light-year is not an appropriate unit to use when extremely high precision is required.

The IAU Style Manual[1] recommends the use of Julian calendar years (not Gregorian) of 365.25 days, or exactly 31,557,600 seconds. This gives the light-year an exact value of 9,460,730,472,580,800 metres.

The light-year is often used to measure distances to stars. In astronomy, the preferred unit of measurement for such distances is the parsec, which is defined as the distance at which an object will generate one arcsecond of parallax when the observing object moved one astronomical unit perpendicular to the line of sight to the observer. This is equal to approximately 3.26 light-years. The parsec is preferred because it can be more easily derived from, and compared with, observational data. However, outside scientific circles, the term light-year is more widely used.

Answer 4

Because miles are just too small to use for such large distances. Measuring the distance to the stars in miles would be like measuring the distance from London to Tokyo in millimeters.

Answer 5

If they were to use meters or miles they'd have to operate with huge numbers all the time. Just a matter of convenience. Also, when the distance unit is related to the speed of light some formulas look kind of more elegant.

Answer 6

3.262 Light Years

Answer 7

Because space is so vast & if you used miles or kilometres, the number would be infinity.

Answer 8

Because of the vastness of space.

Answer 9

Dude ! ask an astronomer !
http://asktheastronomer.blogspot.com

[e-mail]

Answer 10

More convenient---- or --- would you enjoy writing numbers LIKE:
10,017,020,345,096 kilometers

all day long!