The star is located in the Orion constellation, about 640 light-years away from Earth. It's one of the brightest and biggest stars in our galactic neighborhood - if you dropped it in our Solar System, it would extend all the way out to Jupiter, leaving Earth completely engulfed. In stellar terms, it's predicted to explode in the very near future. Of course, the conversion from stellar to human terms is pretty extreme, as Betelgeuse is predicted to explode anytime in the next million years.
But still, whether the explosion occurs in 2011 or 1002011 (give or take 640 years for the light to reach Earth), it's going to make for one of the most unforgettable light shows in our planet's history. For a few weeks, the supernova will be so bright that there will appear to be two stars in the sky, and night be will indistinguishable from day for much of that time. So don't count on getting a lot of sleep when Betelgeuse explodes, because the only sensible thing for the world to do will be to throw a weeks-long global supernova party.
Physicist Brad Carter explains what Earth (and hopefully humanity) can look forward to:
"This is the final hurrah for the star. It goes bang, it explodes, it lights up - we'll have incredible brightness for a brief period of time for a couple of weeks and then over the coming months it begins to fade and then eventually it will be very hard to see at all."
Although there'll be no missing the explosion, Carter points out that the vast majority of material shot out from the supernova will pass by Earth completely unnoticed:
"When a star goes bang, the first we will observe of it is a rain of tiny particles called neutrinos. They will flood through the Earth and bizarrely enough, even though the supernova we see visually will light up the night sky, 99 per cent of the energy in the supernova is released in these particles that will come through our bodies and through the Earth with absolutely no harm whatsoever."
Indeed, just in case anyone is concerned, Betelgeuse is way too far away from Earth to do us any damage. There's been some doomsday speculation of late around the eventual supernova - which might not happen for a million years, it bears repeating - but, as with pretty much all doomsday speculation, you can just ignore it.
In any event, the Betelgeuse explosion will likely be the most dramatic supernova Earth ever witnesses - well, unless our Sun eventually explodes and destroys our planet, which would probably leave Betelgeuse the runner-up. Either way, it isn't the first, as history has recorded the appearance of several so-called "guest stars." Most of these just looked like short-lived stars in the night sky, but some were bright enough to be seen in the day.
The first supernova that history records is thought to have occurred in 185 CE, when a star 8,200 light-years away exploded. Chinese astronomers make explicit note of the sudden appearance of a star and its subsequent disappearance several months later, and the Romans may also have made more cryptic references to it. Astronomers have since located the remnants of the exploded star, confirming the accuracy of the ancient accounts.
The two most dramatic supernova explosions occurred in the 11th century. A supernova in 1006 - you can see its modern remnant above - is the brightest star ever recorded, appearing in the records of China, Egypt, Iraq, Italy, Japan, and Switzerland. There's even some thought that a rock painting by the Hohokam, a Native American tribe in what is now Arizona, represents the first recorded sighting of a supernova in the Americas. Here's the petroglyph in question, which might well record the presence of an unexpected bright light in the sky:
The various observations even allow us to pinpoint what specific type of supernova it was. In all likelihood, it was a Type Ia supernova, which for a few weeks burn as brightly as five billion suns. Astronomer Frank Winkler explains that we can work out from that supposition:
"By knowing this distance and the standard luminosity of Ia supernovae, we can calculate, in retrospect, just how bright the star must have appeared to 11th century observers. On the magnitude scale used by astronomers, it was about minus 7.5, which puts its brightness a little less than halfway between that of Venus and that of the full Moon. And all that light would have been concentrated in a single star, which must have been twinkling like crazy. There's no doubt that it would have been a truly dazzling sight. In the spring of 1006, people could probably have read manuscripts at midnight by its light."
The supernova of 1054 wasn't quite as dramatic, and it seemed to go almost entirely unrecorded in Europe, although there's some thought that records of the new star made by Irish monks got corrupted into allegorical accounts of the Antichrist. Still, the rest of the world saw it just fine, with records popping up in China, Japan, Korea, Persia, and the Americas. Astronomers of the time period wrote that it could be seen in daylight for over three weeks and remained visible in the night sky for nearly two years.
A pair of supernovas in 1572 and 1604 were extensively studied by two generations of legendary astronomers, Tycho Brahe and Johannes Kepler. Since then, the Milky Way hasn't had any supernovas visible from Earth, and so our night sky has remained rather tediously ordinary.
There's about sixteen known candidates in our galaxy for a future supernova explosion, and quite a few of them would have a dramatic effect on our skies. But Betelgeuse is by far one of the closest, and its huge size means its explosion will be particularly dramatic. This is one cosmic disaster that we actually want to see happen sooner than later, because there may never be a sight quite like this ever again.