The giant red star Betelgeuse has gotten 2.5 times fainter since October, according to Villanova University astronomy professor Ed Guinan, writes David Matthews for the New York Daily News.

In his paper, “The Fainting of the Nearby Supergiant Betelgeuse,” Guinan says the star was once the ninth-brightest in the sky but is now 23rd.

The star has been monitored for decades by astronomers and has never dimmed so rapidly in the past.

The star, about 700 light years away from Earth, could be getting ready to go supernova, and if it did, it’d be visible from Earth.

The star would emit a blue glow for three or four months and take about a year to completely fade out.

“It would be a really bright star visible in the daytime,” Guinan said.

But it probably won’t happen in our lifetimes. The star is 9 million years old and stars as large as Betelgeuse don’t usually last beyond 10 million years.

“It’ll probably happen in the next 200,000 or 300,000 years,” Guinan said.

Betelgeuse dims and brightens in cycles, though, so Guinan said it might bounce back.

However, he said, “If it continues dimming, then all bets are off.”

Read more about Betelgeuse’s erratic dimming here.

Listen to an NPR story about Professor Guinan’s Betelgeuse observations here.

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