Betelgeuse and Antares are the two nearest red supergiant stars that are characterized as core-collapse Type-II supernova (SN II) progenitors. Recent photometry shows that Betelgeuse has been declining in brightness since October 2019, and has now reached a modern all-time low of +1.12 mag on December 7, 2019. Betelgeuse is a complicated variable star whose period of ~420 +/-15 days is marginal at best, and this period varies a lot throughout the years. Betelgeuse also has a longer-term (5 - 6 years) and shorter term (100 - 180 days) period of variability with smaller brightness changes. This latest observation has Betelgeuse shining the faintest in the 25+ years of continuous monitoring by astronomers and 50 years of photoelectric V-band spectroscopic observations.
Amateur astronomers around the world have been commenting on the very obvious dimming of one of the key components of the Orion constellation. Many are waiting for Betelgeuse to finally 'go off' which would produce the most fantastic event in modern time astronomy. Indeed, scientists have predicted that Betelgeuse is ripe to go supernova soon, but soon is a relative term, and ranges from 100,000 years and up. No one knows for sure and recent activity may indicate a readiness of the star to enter the pre-supernova phase. Betelgeuse has dipped deeper in brightness before in the 1940's and 50's (long term brightness curve).
Will we see Betelgeuse 'pop' in our lifetime? Probably not, but if it did, you'd certainly know it. No, it would not end life on Earth. No, it won't become a second sun. Betelgeuse is about 450 light years from us and so would appear as a very, very bright star if it exploded. A supernova would need to be less than 50 light years to really affect life on earth. however, when this does happen, Betelgeuse will brighten enormously for a few weeks or months, perhaps as bright as the full moon and visible in broad daylight. And then, Orion will look very different than it does today!
