5289 20230120142955.0 10.1038/s41550-021-01531-9 DOI SCART-2021-0068 Cotton, D.V. Polarimetric detection of nonradial oscillation modes in β Crucis 2022 Here we report the detection of polarization variations due to non-radial modes in the β Cephei star β Crucis. In so doing we confirm 40-year-old predictions of pulsation-induced polarization variability and its utility in asteroseismology for mode identification. In an approach suited to other β Cephei stars, we combine polarimetry with space-based photometry and archival spectroscopy to identify the dominant non-radial mode in polarimetry, f_2, as mode degree l = 3, azimuthal order m = −3 (in the m-convention of Dziembowski) and determine the stellar axis position angle as 25 (or 205) ± 8°. The rotation axis inclination to the line of sight was derived as ~46° from combined polarimetry and spectroscopy, facilitating identification of additional modes and allowing for asteroseismic modelling. This reveals a star of 14.5 ± 0.5 M_⊙ and a convective core containing ~28% of its mass—making β Crucis the most massive star with an asteroseismic age. NO Buzasi, D.L. Aerts, C. Bailey, J. Burssens, S. Pedersen, M.G. Stello, D. Kedziora-Chudczer, L. De Horta, A. De Cat, P. Lewis, F. Malla, S.P. Wright, D.J. Bott, K. Nature Astronomy 6 154--164 peter.decat@observatoire.be 2662622 http://publi2-as.oma.be/record/5289/files/Cotton2022_NatAst6_154.pdf 5462 http://publi2-as.oma.be/record/5289/files/Cotton2022_NatAst6_154.gif?subformat=icon icon 6936 http://publi2-as.oma.be/record/5289/files/Cotton2022_NatAst6_154.jpg?subformat=icon-180 icon-180 published in REFERD