Betelgeuse's hidden companion may be revealing itself

Researchers using Hubble and several ground observatories report spectral and atmospheric patterns consistent with a companion star, nicknamed Siwarha, moving through Betelgeuse's outer layers; astronomers expect a clearer chance to image the companion when it reaches greater separation in November 2027.

Researchers report new evidence that a hidden companion may be affecting Betelgeuse's outer atmosphere. The Center for Astrophysics | Harvard & Smithsonian led observations with NASA's Hubble Space Telescope and ground telescopes over nearly eight years. The team tracked changes in the star's spectrum and in the speed and direction of gases in its outer layers. Those patterns are reported as matching what would be expected from a companion moving through Betelgeuse's atmosphere and leaving a denser wake. Key observations: - The CfA team used Hubble plus ground telescopes at the Fred Lawrence Whipple Observatory (Arizona) and the Roque de los Muchachos Observatory (Spain) to collect data over almost eight years. - Observers recorded changes in Betelgeuse's spectrum and in gas motions that align with a trail of denser material in the star's outer atmosphere. - The trail is interpreted as a wake produced when a companion, nicknamed Siwarha, passes through or in front of Betelgeuse on a long-period orbit, with effects appearing on roughly a six-year cycle. - A separate effort at NASA's Ames Research Center produced a faint image in July that was identified as a candidate for the companion and given the informal name Siwarha. - Earlier work finds two main brightness cycles for Betelgeuse (about 400 days and a roughly six-year secondary period) and attributes the 2020 Great Dimming to a large ejection of hot material from the star's surface. - The new findings were presented at the American Astronomical Society meeting and the study has been accepted for publication by The Astrophysical Journal, according to the reporting. Summary: The reported observations are described as direct signs of a companion shaping Betelgeuse's atmosphere, by producing a wake and matching the timing of a predicted orbit. A clearer, direct image could be easier to obtain when the companion reaches its farthest separation in November 2027, and scientists are continuing observations in the meantime.