How do astronomers define a light year?

Question

Ivy Allen · Accepted Answer

A astronomical unit of distance

A light year is the distance traveled by light in one (1) light year, according to the definition of the astronomical unit of distance. Remember that, Light travells approximately #3.5*10^8# #m/s# Which is that light goes round the Earth #3# times in a fraction of second. WHOOSH!!!!!!!!!!!!!!!! #1# #Light# #year~~9.46*10^12# #km#

Owen Atkinson · Answer

The problem with the definition of light year (ly) is the duration of year. IAU year is Julian 365.25 days of 86400 s/day. An improved ly is for Gregorian 365.2425 days

The approximate value of a light second (ls) is 299792458 meters. A sidereal year is the length of time light travels. The sidereal year is approximated as follows: 365.25 days for the older approximation, 365.2425 days for the later approximation, and 365.256363 days for the more significant digits (sd). In any case, using the standard (tallying) 5-sd approximation of 1 ly = 1.0950 E+11 meters is safe. It is preferable to express the year in days and define day = 86400 s.

Lydia Allen · Answer

undefined A light year is defined as the distance that light travels in one year in a vacuum. It is approximately 9.461 trillion kilometers or 5.879 trillion miles.