Betelgeuse, a red supergiant star in the constellation Orion, is approximately 640 light-years away from Earth. If it were to explode as a supernova, the light from the explosion would travel at the speed of light, which is about 299,792 kilometers per second (or approximately 186,282 miles per second).
Given that Betelgeuse is 640 light-years away, it would take approximately 640 years for the light from the supernova to reach us on Earth. This means that if Betelgeuse were to explode today, we would observe the supernova's light roughly 640 years from now.
It's important to note that while Betelgeuse is a well-known and studied star, it is not currently expected to go supernova in the immediate future. Supernova events are relatively rare and difficult to predict accurately, so we cannot determine precisely when Betelgeuse might explode, if it does at all.