Changing Shape of Betelgeuse
Astronomers have discovered that Sivarha, the companion star of the red supergiant Betelgeuse, moves through Betelgeuse’s outer atmosphere, causing noticeable distortions in the star’s shape and disturbances in its gaseous envelope. Observations conducted between 2021 and 2026 using the VLA and ALMA radio telescopes confirmed the presence of a cool gas layer known as the MOLsphere, along with atmospheric temperatures rising to about 3500 Kelvin. The alterations in Betelgeuse’s atmospheric form appear to correspond directly with Sivarha’s orbital position. However, additional monitoring is required to fully validate these findings.
Located in the Orion constellation, Betelgeuse experienced a dramatic drop in brightness during 2019–2020, an event famously called the Great Dimming. This research, led by Lynn D. Matthews from the Massachusetts Institute of Technology, utilized seven radio frequencies ranging from 22 to 485 GHz via VLA and ALMA telescopes. The gas temperature approximately 2.7 times the star’s radius was measured near 3500 K, while a cooler MOLsphere with temperatures around 2200 K exists between Betelgeuse’s visible surface and its chromosphere.
Interaction with Sivarha
Sivarha orbits at roughly twice Betelgeuse’s radius, traveling through its atmospheric layers. This passage results in Betelgeuse’s atmosphere adopting an oval shape that fluctuates depending on Sivarha’s location along its orbit. Although Sivarha is tens to hundreds of times fainter than the detection limits of radio observations, Betelgeuse’s brightness cycle lasts about 2100 days.
Lynn D. Matthews commented, "The combined power of VLA and ALMA data provided us with compelling evidence."
This breakthrough emphasizes the need for ongoing observations to deepen our understanding of how stars in the Betelgeuse system interact and mutually influence their atmospheres.
Uncovering the dynamic relationship between Betelgeuse and its companion Sivarha offers fresh insights into stellar system behavior. It also highlights the crucial role of multi-frequency radio observations in revealing the complex atmospheric processes within stars. Gaining a better grasp of these phenomena will aid astronomers in studying star evolution and their effects on the surrounding cosmic environment.