If the star Betelgeuse were to explode transiting from the super red giant stage to supernova then our sky would light continuously for two months.

Betelgeuse is the ninth-brightest star in the night sky and second-brightest in the constellation of Orion. Betelgeuse is a star nearing the end of its life. It is likely to crash into a cloud of interstellar dust. If this were to happen, the exploded Betelgeuse will get nearly as bright as the full moon and be visible for two or three months in broad daylight.

A star explodes by running out of nuclear fuel. By running out of nuclear fuel a lot of its mass reaches the core. Eventually, the core becomes so heavy it cannot withstand its gravitational force. The core collapses, resulting in the giant explosion of a supernova.

When astronomers say Betelgeuse is expected to explode soon, they mean shortly in astronomical terms– within a million years. So “soon” could be hundreds of thousands of years from now, which is a short amount of time compared to the universe, but no concern for us. Even if Betelgeuse were to explode, at our distance, we wouldn’t be in any danger because the vast amount of energy released by a supernova will be spread over a bubble of space with a surface area of more than a million square light years.

Sources:

http://www.space.com/22009-betelgeuse.html

http://www.daviddarling.info/encyclopedia/B/What_will_happen_when_Betelgeuse_explodes.html