Light-year
noun, suffix
What happens when light travels a year? You have a light-year.
光年 is typically used after a number to specify the vast distances between celestial objects, like 地球からこの星まで3光年です (it's 3 light-years from Earth to this star).
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
1光年
one light year
1.19光年
1.19 light years
150光年
150 light years
月からニ光年先に小さい石が見える。
You can see a small rock two light years away from the moon.
このロケットで一光年先に行くとすると一万年はかかります。
With this rocket it would take at least take 10,000 years to travel one light year.
一光年はセグウェイで何日かかるんだろう。
I wonder how many days it would take to travel one light year on a Segway.