Scientists Think That Betelgeuse – A Huge Star in Orion – Might Be Dimming Because it’s About to Explode into a Supernova
One of the brightest stars in our sky is the dimmest it has been in 100 years, according to a report in National Geographic. The decline happened rapidly: in October, scientists first registered a decrease in brightness. By December, the star Betelgeuse had faded so much that it didn't even number among the "top 20" list of brightest stars in the sky. (It's normally in or near the top ten.)
"The outline of Orion is noticeably different with Betelgeuse so faint," revealed Villanova University astronomy professor Dr. Edward Guinan, who has been tracking the star's waning brightness.
Betelgeuse is one of the brightest stars in the constellation Orion, about 600 light-years away from Earth, and it is one of the largest stars we have measured: 700 times the size of our Sun, with 20 times the mass.
Although many stars wax and wane in brightness, they don't suddenly fade out so suddenly like this. Astronomers suspect that Betelgeuse is near the end of its life cycle and will soon explode into a supernova – one big enough and bright enough to outshine the full moon in the night sky.
A supernova is the dying explosion of a star with at least five times the mass of the Sun. As these stars run out of fuel to burn, they cool off and the pressure drops – FAST. The star's gravity rapidly telescopes in on itself, which triggers a shock wave in the outer layers that creates the explosion we call a supernova.
It is this precipitating collapse and drop in mass that scientists think we could be witnessing, as well as an attendant cloud of billowing dust and debris that would shroud the dying star from view. That said, scientists caution that – since we have only been steadily monitoring the star since the 1920s – it's still hard for us to say what "normal" is. Many historic observations of the star record periods of pronounced dimming, followed by a gradual return to brightness.
It's another case of wait-and-see. If the star grows slowly but steadily brighter, we just witnessed a significant (but not unusual) dip. And, if it continues to fade, all bets are off. Since the light we see from the star takes 600 years to reach Earth, we could witness a supernova tomorrow that actually happened in the Middle Ages... Or, 600 years from now, humans will watch one that we had no idea actually started today.
Image: NASA, ESA, N. Smith (University of Arizona, Tucson), and J. Morse (BoldlyGo Institute, New York) CC BY 4.0