Betelgeuse, a dying star, holds a mystery that intrigues scientists.
Not long ago, the star’s sudden dimming caught everyone’s attention. However, that mystery has been mostly unraveled. Yet, even before this event, researchers noticed something unusual. They found that Betelgeuse seemed to be spinning at a speed of 5 kilometers per second.
This finding puzzled astronomers. According to theories, stars as old as Betelgeuse should spin much slower. So, the question arose: what’s causing this discrepancy?
Recent studies offer a fascinating explanation. Jing-Ze Ma from the Max Planck Institute for Astrophysics and his team propose that Betelgeuse’s surface turmoil might create the illusion of rapid rotation.
Stars rotate at different speeds, which scientists measure by observing the light they emit. Light from a star’s side moving towards us shifts towards the blue spectrum, while light from the receding side shifts to red. This shift helps determine the star’s rotation speed.
However, Betelgeuse is not a typical star. It’s a red supergiant nearing the end of its life, with a surface that’s constantly in motion due to convection.
This star’s surface activity is intense. Hot material rises, cools, then sinks, on a scale much larger than what we see on our Sun. In Betelgeuse’s case, these convection cells can be as vast as the distance between the Earth and the Sun.
To explore this further, Ma and his colleagues turned to 3D simulations. They modeled non-rotating red supergiants and analyzed the results as if observed by the Atacama Large Millimeter/submillimeter Array (ALMA).
Their findings were revealing. The simulations showed that the movement within these giant stars could mimic rotation. In fact, in 90% of the simulations, the data resembled that of a star rotating at several kilometers per second.
This doesn’t conclusively prove that Betelgeuse isn’t spinning quickly. However, it suggests that current observations might not be enough to determine its rotation speed. More detailed studies are underway, which could provide clearer insights.
The implications are significant. If Betelgeuse is indeed spinning rapidly, it might have absorbed a smaller star. If not, it teaches us to be more cautious in interpreting data from unstable stars.
Astronomers like Andrea Chiavassa emphasize our limited understanding of massive, turbulent stars like Betelgeuse. They highlight the importance of improving simulations and the need for data from advanced telescopes like ALMA.
This research, published in The Astrophysical Journal Letters, opens new paths to understanding the mysteries of stars like Betelgeuse.