Giant star Betelgeuse already exploded? Betelgeuse is a supergiant star (with about 19 times solar mass and about 1000 times solar radius) in a distance of about 550 light years from Earth. It's a runaway star moving through the interstellar medium at a speed of 30 km/s. At near-infrared wavelengths, it is the brightest star in the night sky. Astronomers expect Betelgeuse to end its evolution any moment with a supernova explosion. When Betelgeuse explodes, it will shine as bright as the half-Moon, for more than three months. Life on Earth will be unharmed. Since it is 550 light years distant, then it already may have exploded, but the light hasn't reached us yet. How to be sure? See also https://moviecultists.com/has-betelgeuse-already-exploded