The speed of light in a vacuum is defined to be exactly 299,792,458 metres per second (or 1,079,252,848.8 km/h, which is approximately 186,282.397 miles per second, or 670,616,629.4 miles per hour)
The distance that light travels in a year is so large that it is a useful unit of distance in astronomy:
* Light Year: the distance that light travels (through a vacuum) in one year (9.46 x 10^17 cm).
* The nearest star (other than the Sun) is 4.3 light years away.
* Our galaxy (the Milky Way) is about 100,000 light years in diameter.
* The distance to the galaxy M87 in the Virgo cluster is 50 million light years.
* The distance to most distant object seen in the universe is about 18 billion light years (18 x 10^9 light years)
lol well there you go this is copied from a few websites and several websites had this same information so i believe it to be 99% correct could still be wrong cause i got it off the net after all