What is a light year in the science of astronomy?

Question

In the science of astomomy, please explaine to this lay person the meaning of a light year.

Answer 1

A light year is the distance that light will travel in a year, or 9.46053E+15 meters. That's 63239.7 times further than the distance between Earth and the sun.

Answer 2

A light-year or lightyear (symbol: ly) is a unit of measurement of length, specifically the distance light travels in vacuum in one Julian year.


A light-year is equal to:

* 9,460,730,472,580.8 km (about 9.461 Pm)
* about 5,879,000,000,000 statute miles
* about 63,240 astronomical units, where 1 AU is the average distance between the centers of the Earth and the Sun.
* about 0.3066 parsecs, where a parsec is defined as the distance at which a star would shift in parallax by an arcsecond as the Earth orbited the Sun.

The actual, 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 24 hours). This is the value recommended by the IAU. However, other reference years are often used (e.g. Yahoo's calculator uses a smaller value than the IAU), such that the light-year is not an appropriate unit to use when extremely high precision is required.

The IAU style guide [1] recommends the use of calendar years, specifically Julian (and not Gregorian) calendar years 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, again about 9.461 Pm).

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 3

It refers to the distance travelled by light in a year

Answer 4

The light year is the distance made by light in one year.

Answer 5

The distance that light travels in one year. Which is 9.46 trillion kilometers or 5.88 trillion miles. Light travels at a speed of 299.792 kilometers per second.

Answer 6

It's the distance light travels in a year.
Light travels at 186,000 miles a second.
To work out how far it travels in a year you multiply that by 60, and you have how fast it travels in a minute.
Then muliply by 60 again - hour
Multiply that by 24 - day
Then multiply by 365 to work out how far it travels in a year.
It's a very long way!

Answer 7

It is a measure of distance that is equal to the distance that light travels in a year.

Answer 8

One light year is the distance light moves in one year. It's equal to 5.87-trillion miles (9.46-trillion kilometers)

Answer 9

Light year is how far light travels in one year. About 9.46 trillion kilometers. or 5.88 trillion miles.
That's 5,880,000,000,000 miles traveled in one year. Whew!
OK?.................OK.
To get light speed per second, divide that by 365, then divide that by 24, then divide that by 60, then divide that by 60.

Answer 10

Here is a good explanation for you.

http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html