Question

The star Betelgeuse is about 600 light-years away. If it explodes tonight,

-we'll know because it will be brighter than the full Moon in the sky.
-we'll know because debris from the explosion will rain down on us from space.
-we won't know about it until about 600 years from now.

Answer 1

-we won't know about it until about 600 years from now.

Step-by-step explanation:

The speed of light is about 300,000_Km/s

A light-year is a distance unit. It is the distance travelled at the speed of light in a year. So in one year, the distance covered is about 10 trillion km.