Abstract
The orbits of binary stars precess as a result of general relativistic effects, forces arising from the asphericity of the stars, and forces from any additional stars or planets in the system. For most binaries, the theoretical and observed precession rates are in agreement1. One system, however—DI Herculis—has resisted explanation for 30 years2,3,4. The observed precession rate is a factor of four slower than the theoretical rate, a disagreement that once was interpreted as evidence for a failure of general relativity5. Among the contemporary explanations are the existence of a circumbinary planet6 and a large tilt of the stellar spin axes with respect to the orbit7,8. Here we report that both stars of DI Herculis rotate with their spin axes nearly perpendicular to the orbital axis (contrary to the usual assumption for close binary stars). The rotationally induced stellar oblateness causes precession in the direction opposite to that of relativistic precession, thereby reconciling the theoretical and observed rates.
Similar content being viewed by others
References
Claret, A. & Giménez, Á. The apsidal motion test of the internal stellar structure—comparison between theory and observations. Astron. Astrophys. 277, 487–502 (1993)
Martynov, D. I. & Khaliullin, K. F. On the relativistic motion of the periastron in the eclipsing binary system DI Herculis. Astrophys. Space Sci. 71, 147–170 (1980)
Guinan, E. F. & Maloney, F. P. The apsidal motion of the eccentric eclipsing binary DI Herculis—an apparent discrepancy with general relativity. Astron. J. 90, 1519–1528 (1985)
Claret, A. Some notes on the relativistic apsidal motion of DI Herculis. Astron. Astrophys. 330, 533–540 (1998)
Moffat, J. W. The orbital motion of DI Herculis as a test of a theory of gravitation. Astrophys. J. 287, L77–L79 (1984)
Hsuan, K. & Mardling, R. A. A Three body solution for the DI Her system. Astrophys. Space Sci. 304, 243–246 (2006)
Shakura, N. I. On the apsidal motion in binary stars. Sov. Astron. L, 224–226 (1985)
Company, R., Portilla, M. & Giménez, Á. On the apsidal motion of DI Herculis. Astrophys. J. 335, 962–964 (1988)
Popper, D. M. Rediscussion of eclipsing binaries. XIII—DI Herculis, a B-type system with an eccentric orbit. Astrophys. J. 254, 203–213 (1982)
Perruchot, S. et al. The SOPHIE spectrograph: design and technical key-points for high throughput and high stability. SPIE Conf. Ser. 7014 10.1117/12.787379 (2008)
Holt, J. R. Spectroscopic determination of stellar rotation. Astron. Astrophys. 12, 646 (1893)
Rossiter, R. A. On the detection of an effect of rotation during eclipse in the velocity of the brighter component of beta Lyrae, and on the constancy of velocity of this system. Astrophys. J. 60, 15–21 (1924)
McLaughlin, D. B. Some results of a spectrographic study of the Algol system. Astrophys. J. 60, 22–31 (1924)
Albrecht, S., Reffert, S., Snellen, I., Quirrenbach, A. & Mitchell, D. S. The spin axes orbital alignment of both stars within the eclipsing binary system V1143 Cyg using the Rossiter-McLaughlin effect. Astron. Astrophys. 474, 565–573 (2007)
Queloz, D. et al. Detection of a spectroscopic transit by the planet orbiting the star HD209458. Astron. Astrophys. 359, L13–L17 (2000)
Winn, J. N. et al. Measurement of spin-orbit alignment in an extrasolar planetary system. Astrophys. J. 631, 1215–1226 (2005)
Gray, D. F. The Observation and Analysis of Stellar Photospheres 3rd edn (Cambridge Univ. Press, 2005)
Markwardt, C. B. Non-linear least squares fitting in IDL with MPFIT. Preprint at 〈http://arXiv.org/abs/0902.2850〉 2009
Press, W. H., Teukolsky, S. A., Vetterling, W. T. & Flannery, B. P. Numerical Recipes in C. The Art of Scientific Computing 2nd edn 689–699 (Cambridge Univ. Press, 1992)
Von Zeipel, H. The radiative equilibrium of a slightly oblate rotating star. Mon. Not. R. Astron. Soc. 84, 684–701 (1924)
Guinan, E. F., Marshall, J. J. & Maloney, F. P. A new apsidal motion determination for DI Herculis. Inform. Bull. Variable Stars 4101, 1–44 (1994)
Fabrycky, D. & Tremaine, S. Shrinking binary and planetary orbits by Kozai cycles with tidal friction. Astrophys. J. 669, 1298–1315 (2007)
Chelli, A. & Petrov, R. G. Model fitting and error analysis for differential interferometry. II. Application to rotating stars and binary systems. Astron. Astrophys. 109 (Suppl.). 401–415 (1995)
Le Bouquin, J. B. The spin-orbit alignment of the Fomalhaut planetary system probed by optical long baseline interferometry. Astron. Astrophys. 498, L41–L44 (2009)
Reisenberger, M. P. & Guinan, E. F. A possible rescue of general relativity in DI Herculis. Astron. J. 97, 216–221 (1989)
Van Dien, E. Axial rotation of the brighter stars in the Pleiades cluster. J. R. Astron. Soc. Can. 42, 249–261 (1948)
Acknowledgements
We are grateful to Á. Giménez, E. Guinan and T. Mazeh for bringing DI Herculis to our attention. We thank J. Lub, R. Tubbs, C. Hopman, Y. Levin and D. Fabrycky for discussions about double stars and their properties. We also thank H. Reckman for essential help during one observing run. We are grateful to the Sophie team for building the spectrograph and reduction pipeline. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France, and the Vienna Atomic Line database (VALD) located at http://ams.astro.univie.ac.at/vald/. S.A. acknowledges support during part of this project by a Rubicon fellowship from the Netherlands Organisation for Scientific Research (NWO). J.N.W. acknowledges support from a NASA Origins grant (NNX09AD36G). S.A. and S.R. acknowledge funding from the Optical Infrared Coordination network (OPTICON).
Author Contributions S.A. participated in the development of the concept of this research and the analysis code, participated in the observations, the analysis and interpretation of the data and writing the manuscript. S.R. participated in the development of the concept of this research and the analysis code and the observations. I.A.G.S. participated in the analysis and interpretation of the data and in writing the manuscript. J.N.W. participated in the analysis and interpretation of the data and in writing the manuscript.
Author information
Authors and Affiliations
Corresponding author
Supplementary information
Supplementary Figures
This file contains Supplementary Figures 1-3 with Legends. (PDF 247 kb)
Rights and permissions
About this article
Cite this article
Albrecht, S., Reffert, S., Snellen, I. et al. Misaligned spin and orbital axes cause the anomalous precession of DI Herculis. Nature 461, 373–376 (2009). https://doi.org/10.1038/nature08408
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1038/nature08408
- Springer Nature Limited
This article is cited by
-
Relativistic gravitational force
Celestial Mechanics and Dynamical Astronomy (2023)
-
Distinguishing spin-aligned and isotropic black hole populations with gravitational waves
Nature (2017)
-
Gravitational analysis of V541 Cygni, DI Herculis, and the Pioneer anomaly
Astrophysics and Space Science (2011)
-
A new concept for the combination of optical interferometers and high-resolution spectrographs
Experimental Astronomy (2010)
-
Research highlights
Nature Physics (2009)