Among celestial bodies, Betelgeuse stands out as particularly peculiar, yet scientists have now elucidated a long-standing enigma associated with this star. The existence of a diminutive stellar companion has been definitively established, its presence inferred from the disturbance it engenders as it navigates through the expansive atmosphere of the red supergiant.
When its luminosity is not obscured by transient ejections of dust, Betelgeuse’s light exhibits variations attributable to two separate cyclical patterns. One such cycle, with a duration of approximately 400 days, has been correlated with internal oscillatory movements. The second cycle, however, spans around 2,100 days and has presented a considerably greater challenge to astrophysical explanation.
The predominant hypothesis posited the presence of a small, faint companion star in a close orbital path around the red giant, with observational data leading to a probable detection last July. Betelgeuse’s stellar associate has now received unequivocal confirmation, several months subsequent to the formal acceptance of its proposed designation, Siwarha.
An exhaustive analysis of nearly eight years of photometric and spectroscopic data, gathered through observations from the Hubble Space Telescope, the Fred Lawrence Whipple Observatory situated in Arizona, and the Roque de Los Muchachos Observatory in the Canary Islands, Spain, furnished ample substantiation for the existence of a secondary star, evidenced by its distinct ‘wake’ in the form of a high-density filament of gas within Betelgeuse’s distended atmosphere.
“It bears a resemblance to a vessel traversing water. The companion star generates a ripple effect within Betelgeuse’s atmospheric envelope, which is demonstrably discernible in the collected data,” stated Andrea Dupree, an esteemed astronomer affiliated with the Harvard & Smithsonian Center for Astrophysics (CfA).
“For the first time, we are observing tangible indicators of this wake, or gaseous trail, thereby validating the presence of a concealed companion star influencing Betelgeuse’s visual characteristics and observable behavior.”
Rather than diminishing Betelgeuse’s luminosity, Siwarha exerts its influence by modifying the red supergiant’s spectral profile, particularly affecting the ultraviolet wavelengths emitted by ionized iron. When the companion star is situated in front of Betelgeuse, a pronounced peak is observed in the iron-emitted light. Conversely, following Siwarha’s passage, or eclipse, its trailing plume of gas begins to absorb these specific wavelengths, resulting in a truncated peak. This phenomenon gradually dissipates until Siwarha completes another orbital revolution, approximately 2,109 days, or roughly 5.77 years, later.
“With this newly acquired direct observational evidence, Betelgeuse affords us an unparalleled vantage point to scrutinize the temporal evolution of a colossal star,” commented Dupree.
“The discovery of the wake generated by its celestial counterpart now enables us to comprehend the mechanisms by which such stars develop, eject material, and ultimately undergo supernova explosions.”
Siwarha has now receded behind Betelgeuse and is not anticipated to reappear until August of 2027.
