While they seem to be eternal, even stars have a lifespan. At the end of this lifespan they can die in several ways depending on their mass. Perhaps the most spectacular star death is the one experienced by stars between 60 and 130 solar masses, a supernova. This explosion is the biggest and most violent that exists in the universe and creates so much light that it can outshine an entire galaxy.
Due to this incredible brightness, these explosions can be observed from millions of light-years away in galaxies far beyond the Milky Way with the help of powerful telescopes. However, if a star in our own galaxy would ever explode in this fashion, we would all see it with the naked eye. Fortune has it that Betelgeuse might just be such a star.
Betelgeuse is dimming, again!
Betelgeuse is one of the stars that make up the constellation Orion, the bright red star that is its shoulder to be precise. It is a red supergiant, a star that is about 700 times the size of our Sun, and as you might have heard in recent news, it is dimming.
Now this dimming is not necessarily anything new, as this star has had a variable brightness for thousands of years to the extent where ancient Greeks and Aboriginal Australians have noticed this. What is special about this dimming is that it the star became about 6.5x dimmer than usual, which is much more than anything that has been recorded in the last century of measurements. Does this mean that it will blow up any time soon? Astronomers don’t think so, they postulate that it is caused by several cycles overlapping for the first time in many centuries.
What could be seen if Betelgeuse did blow up?
Still, it is interesting to wonder what one could see if Betelgeuse did blow up. And this is exactly what Jared Goldberg and Evan Bauer from the University of California, Santa Barbara (UCSB) did. They used a specialized stellar evolution code called MESA+STELLA to run many simulations of Betelgeuse under different parameters and then calculated how this would look from earth. Their results were not disappointing!
How bright will #Betelgeuse be when it blows up? Moon-ish brighness for 3+ months, seen during the daytime for about a year, brighter than the star now for ~2 years, naked eye visible for ~3 years. Credit: @UCSBPhysics grad students Jared Goldberg and Evan Bauer using MESA. 1/ pic.twitter.com/X8m0VdYvDF
— Andy Howell (@d_a_howell) February 4, 2020
In every simulation, the brightness is at least 10 times brighter than Venus and at best about half the brightness of a full Moon. This means that for about three months we would have a very bright star in the sky that would be capable of casting shadows during the day and be bright enough to read under at night. After that it would dim, but not disappear completely. We would see it for about a year, after which it would finally disappear forever from our view.
People need not worry about any radiation or fallout from this star, though. At a distance of more than 700 light-years, we are completely in the clear and ready to enjoy the fireworks if indeed it did take place within our lifetimes.