“The giant’s shoulder” has returned to the night sky.
Look east a couple of hours after sunset—when it’s properly dark—and you can witness the rising of the red supergiant star Betelgeuse, the second brightest star in the constellation of Orion and one of the brightest stars in the night sky.
Or, at least, it was until two periods of dimming, shape-shifting and “burping” a year ago and again earlier this year.
That dimming—which caused some to wonder if Betelgeuse might explode as a supernova sooner than expected was thought to be caused by cooling or dust—was well publicised.
A study published in the Astrophysical Journal says that it was also due to the pulsations of Betelgeuse caused by pressure waves.
The same scientists also say that the giant red star is smaller and closer to our Solar System than previously thought.
How can that be?
“It’s normally one of the brightest stars in the sky, but we’ve observed two drops in the brightness of Betelgeuse since late 2019,” said Dr. Meridith Joyce from the Australian National University (ANU).
At one stage Betelgeuse appeared just 36% of its normal brightness. It’s currently at 81%.
“We know the first dimming event involved a dust cloud … we found the second smaller event was likely due to the pulsations of the star,” said Joyce. The researchers used hydrodynamic and seismic modelling to learn more about the physics driving its pulsations to see what phase of its life Betelgeuse is in.
The upshot is that Betelgeuse has gotten a new lease on life; the study predicts that it may be another 100,000 years until it dies in a fiery explosion after the inevitable collapse of its core.
Stars with a mass more than ten times that of our Sun—such as Betelgeuse—end their life in a supernova, a colossal stellar explosion that forms heavy elements like iron and manganese.
“It’s burning helium in its core at the moment, which means it’s nowhere near exploding,” said Joyce. “We could be looking at around 100,000 years before an explosion happens.”
Perhaps more surprisingly, the study shows that Betelgeuse is both smaller and closer to the Solar System than previously thought. Formerly thought to be bigger than the orbit of Jupiter is in our Solar System and between 650 and 750 light years away, the researchers now think that it’s only two-thirds of that size and just 530 light-years from us.
So the closest supernova candidate star just got smaller and closer—but it’s still too far away to have any effect on us on the off-chance is does go supernova.
Wishing you clear skies and wide eyes.