Betelgeuse was at one point so huge that it would reach out to Jupiter's orbit. Over the past 15 years the giant has begun a massive contraction. It's size has dropped by 15% although the brightness has not diminished perceptibly.
Red giants often have very short lifespans, mostly only a few million years. They go off main sequence and start their helium, carbon and on to more massive elements until they reach iron where fusion stops. But between the first contraction and the end of fusion, series of contractions often take place which re-energizes and restarts the fusion process. Though scientists do not know why Betelgeuse is contracting, it could be one of these contractions that happens as the massive stars switch fuels for fusing.
A supernova happening in Earth's vicinity is scientifically interesting but too close could prove to be a disaster to Earth, as a gama-ray pulse could end life on Earth. Betelgeuse however is 600 light years distant and so is too distant to do any harm.
Check out the full Daily Galaxy article