The view would be mind-boggling, day or night. The Orion constellation can be seen from nearly everywhere on Earth, which means nearly everyone could see the exploding star. It would easily cut through the artificial-light pollution that prevents 80 percent of the world—and a staggering 99 percent of the United States and Europe—from experiencing a clear view of the night sky.
“At the predicted brightness of a Betelgeuse supernova, you could be standing in the center of the biggest city in the world, and you would certainly see it,” says John Barentine, an astronomer and the director of public policy at the International Dark-Sky Association, a nonprofit that works to mitigate light pollution. “You couldn’t miss it.”
Even more spectacular, the display would stick around. The gleaming orb would remain visible for more than a year, perhaps even longer. How strange it would be to witness day in and day out, to understand, for the most part, that the blaze is simply a natural wonder of the universe, but still feel, on a deeper, more primitive level, that the sky looks very wrong.
The supernova wouldn’t harm Earth. Betelgeuse isn’t the sort of star whose demise would produce radiation that could roil the planet’s atmosphere. At about 650 light-years from here, Betelgeuse is nearby on a cosmic scale, but thankfully not close enough to cause any damage.
Read: What if history’s brightest supernova exploded in Earth’s backyard?
So how might people react? Judging by what happened in New York about a year ago, there would be confusion, even panic. One night in December, an aquamarine glow appeared over Queens, prompting 3,200 calls to 911 in half an hour. Residents shared videos and photos of the ghostly spectacle on social media, along with guesses for the source. Was this a bomb? Was it the climax of a ground-shaking battle between superheroes?
The real explanation was far less dramatic. The operator of an electrical-power plant quickly chimed in on social media to describe the incident. Some equipment at the facility had short-circuited, and the malfunction sent a powerful current shooting into the air. The electricity jostled atoms of gas in the atmosphere, prompting them to emit blue light.
A similar scenario would likely play out online in the case of a surprise supernova, with NASA and other science institutions leading the awareness campaign. “The way the world is on edge about a number of things right now, whether it’s climate change or international relations, it would be interesting how people would interpret it, if some people would think that it was some kind of sign,” Barentine says.
The most recent nearby supernova appeared long before people could panic about it on Twitter, in 1987, but it could be seen only in very dark parts of the Southern Hemisphere, far from artificial lights. Other examples are found even deeper in history, in 1604 and 1054. Betelgeuse would provide a far better show; the other stars were thousands of light-years from Earth, rather than hundreds.