The star Betelgeuse has been a bit of a drama queen lately, dimming twice in the past year. Now astronomers say they’ve found what may have caused the latest episode – and in so doing, also discovered that the star is smaller, closer to Earth and further from exploding than previously thought.
Shining from the shoulder of the constellation of Orion, Betelgeuse is one of the brightest stars in the night sky. Well, most of the time, anyway – in late 2019 it dimmed so drastically that many suspected it was about to go supernova. By April 2020 it had returned to its former glory, but that didn’t last long. Within a few months it started to dim again, albeit not quite as intensely as the first time.
It’s believed that the cause of the first dimming event was a dust cloud, expelled by the star and temporarily blocking the light from reaching us. And now researchers on the new study believe they have an explanation for the second episode.
By conducting hydrodynamic and seismic simulations of the star’s surface, the team found that pulsations caused by pressure waves would have created the kind of dimming that was observed. This helped the team determine which phase of its life Betelgeuse is currently in. And it’s good news for the star, but bad news for anyone who was hoping for a celestial fireworks display.
"It's burning helium in its core at the moment, which means it's nowhere near exploding," says Dr. Meridith Joyce, lead author of the study. ”We could be looking at around 100,000 years before an explosion happens."
But that’s not the most interesting discovery that the study made. This modelling also allowed the team to revise the size of the star and its distance from Earth. It turns out that it’s a little smaller and closer to us than we realized previously.
"The actual physical size of Betelgeuse has been a bit of a mystery – earlier studies suggested it could be bigger than the orbit of Jupiter,” says Dr László Molnár, co-author of the study. “Our results say Betelgeuse only extends out to two thirds of that, with a radius 750 times the radius of the Sun. Once we had the physical size of the star, we were able to determine the distance from Earth. Our results show it's a mere 530 light years from us - 25 percent closer than previous thought."
While it may be natural to feel a little on edge about this volatile star being even closer to us, the team says that it’s still too far away for its eventual supernova to do any damage to Earth.
The research was published in the Astrophysical Journal.
Source: Australia National University
