Astronomers are investigating whether the dramatic dimming of a giant star means it's getting ready to explode.
The red supergiant star Betelgeuse marks Orion's right shoulder. As the star nears its end, it's expanded to nearly 900 times wider than the sun and is normally one of the brightest stars in the sky.
However it's recently dimmed by a factor of two to a "modern all-time low" magnitude, leading to speculation it could be about to end in a spectacular supernova.
As NASA explains, a supernova is the extremely bright, super-powerful explosion of a star - "the biggest explosion that humans have ever seen".
"Anyone have any thoughts on whether this means it's Betelgeuse's time? To go SUPERNOVA, that is?!?" one person wrote on Reddit.
"I mean, it is supposed to shrink once it starts fusing iron, right? And shrinking means that it's getting dimmer, right? Could this be what we've all been waiting for for years?"
However astronomers studying it say it's likely part of a pattern of brightening and dimming stars go through in the later phases of their life.
"No, this doesn't mean it's about to blow. It's a variable star and deep dimmings have happened before. Likely it won't explode for 100,000 years or so," wrote science expert Dr Phil Plait on Twitter.
"It has several cycles all going on at the same time in its atmosphere, and (I'm guessing) it's possible they just are all kinda hitting their low. I strongly doubt this has anything to do with it getting ready to explode, though."
"It's not even the star closest to going supernova - that honor goes to Eta Carinae," astronomer Yvette Cendes of the Harvard-Smithsonian Center for Astrophysics wrote on Reddit.
When it does eventually blow, it will brighten to the point it will be visible in daylight.
"At 650 light-years away it's too far to hurt us even if it does go supernova. It'll get as bright as the full Moon though! That'll be cool (though irritating for astronomers who want to observe other objects)," Dr Plait wrote.
"So don't panic. At least not until you see astronomers buying lots of survival supplies. :) But Betelgeuse almost certainly isn't a threat."
