Letter | Published:

Vigorous atmospheric motion in the red supergiant star Antares

Nature volume 548, pages 310312 (17 August 2017) | Download Citation



Red supergiant stars represent a late stage of the evolution of stars more massive than about nine solar masses, in which they develop complex, multi-component atmospheres. Bright spots have been detected in the atmosphere of red supergiants using interferometric imaging1,2,3,4,5. Above the photosphere of a red supergiant, the molecular outer atmosphere extends up to about two stellar radii6,7,8,9,10,11,12,13,14. Furthermore, the hot chromosphere (5,000 to 8,000 kelvin) and cool gas (less than 3,500 kelvin) of a red supergiant coexist at about three stellar radii15,16,17,18. The dynamics of such complex atmospheres has been probed by ultraviolet and optical spectroscopy19,20,21,22. The most direct approach, however, is to measure the velocity of gas at each position over the image of stars as in observations of the Sun. Here we report the mapping of the velocity field over the surface and atmosphere of the nearby red supergiant Antares. The two-dimensional velocity field map obtained from our near-infrared spectro-interferometric imaging reveals vigorous upwelling and downdrafting motions of several huge gas clumps at velocities ranging from about −20 to +20 kilometres per second in the atmosphere, which extends out to about 1.7 stellar radii. Convection alone cannot explain the observed turbulent motions and atmospheric extension, suggesting that an unidentified process is operating in the extended atmosphere.

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We thank the ESO VLTI team for supporting our VLTI/AMBER observations. This work is based on AMBER observations made with the VLTI of the ESO (program ID: 093.D-0468A/B). K.O. acknowledges the grant from the Universidad Católica del Norte.

Author information


  1. Instituto de Astronomía, Universidad Católica del Norte, Avenida Angamos 0610, Antofagasta, Chile

    • K. Ohnaka
  2. Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany

    • G. Weigelt
    •  & K.-H. Hofmann


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K.O. wrote the telescope proposal and the first draft of the paper, carried out the observations, data reduction, and image reconstruction, and worked on data interpretation. G.W. and K.-H.H. were co-authors on the telescope proposal and worked on data reduction and interpretation.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to K. Ohnaka.

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