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Beteigeuze's companion makes waves

14.1.2026

Translation: machine translated

Using the Hubble Space Telescope and other instruments, the suspected companion of Betelgeuse has now also been detected spectroscopically, as it is trailing a wave in the extended atmosphere of the stellar giant.

With the help of data from the Hubble Space Telescope (HST) and other Earth-based instruments, a group led by Andrea Dupree from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, was able to indirectly detect the long-suspected companion of the red supergiant Betelgeuse in the constellation of Orion for the first time using spectroscopy. During its orbital period of around six years, it moves through the extremely extended atmosphere of the stellar giant and produces a pronounced wave that is noticeable in Betelgeuse's spectrum.

To this end, Dupree's team spent eight years observing the reddish star, which is clearly visible to the naked eye, in the shoulder of the celestial giant Orion using the HST and telescopes from the Fred Lawrence Whipple Observatory and the Roque de Los Muchachos Observatory. The astronomers were particularly interested in the spectral lines of the singly charged iron (Fe II) in the ultraviolet wavelength range. Visible changes can be seen there, which are generated by the orbit of the companion around the red supergiant.

If the companion with its bow wave is in front of Betelgeuse from our point of view, the Fe II spectral lines are slightly shifted into the blue, i.e. to shorter wavelengths in the ultraviolet. If, on the other hand, it is behind the giant star, the spectral lines appear at slightly longer wavelengths, i.e. they are red-shifted. These changes occur at a rhythm of 2100 days, which corresponds to around 5.7 years.

The wave of the companion in the spectrum | In the ultraviolet at a wavelength of about 2725 Angstromsm or 273 nanometres, the Hubble Space Telescope was able to detect the orbit of Betelgeuse's companion in the region of the spectral lines of singly ionised iron (Fe II). The companion star generates a pronounced wave in the outer atmosphere of the stellar giant, which can be detected spectroscopically. Within six years, which corresponds to the orbital period of the companion, the spectral lines of the wave are shifted into the blue as it moves towards us and into the red as it moves away from us.
Source: © Illustration: NASA, ESA, Elizabeth Wheatley (STScI); Science: Andrea Dupree (CfA) / Betelgeuse: Effect of Companion Star Wake (Ausschnitt)

Beteigeuze is located about 650 light years away from us in the constellation Orion and has about 400 million times the volume of our sun. If the red supergiant could be transported into our solar system, it would extend beyond the orbit of Jupiter and would have long since devoured the inner rocky planets «» . Betelgeuse is one of the closest stars to us that will explode as a supernova in an astronomically short period of time. It would then shine considerably brighter than Venus in our sky. But no one can say for sure when this will happen.

Spectrum of Science

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Original article on Spektrum.de

Header image: © Artwork: NASA, ESA, Elizabeth Wheatley (STScI); Science: Andrea Dupree (CfA) / Betelgeuse and Wake of its Companion Star (Artist's Concept) (detail)

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