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Spin alignment of stars in old open clusters


Stellar clusters form by gravitational collapse of turbulent molecular clouds, with up to several thousand stars per cluster1. They are thought to be the birthplace of most stars and therefore play an important role in our understanding of star formation, a fundamental problem in astrophysics2,3. The initial conditions of the molecular cloud establish its dynamical history until the stellar cluster is born. However, the evolution of the cloud’s angular momentum during cluster formation is not well understood4. Current observations have suggested that turbulence scrambles the angular momentum of the cluster-forming cloud, preventing spin alignment among stars within a cluster5. Here we use asteroseismology68 to measure the inclination angles of spin axes in 48 stars from the two old open clusters NGC 6791 and NGC 6819. The stars within each cluster show strong alignment. Three-dimensional hydrodynamical simulations of proto-cluster formation show that at least 50% of the initial proto-cluster kinetic energy has to be rotational in order to obtain strong stellar-spin alignment within a cluster. Our result indicates that the global angular momentum of the cluster-forming clouds was efficiently transferred to each star and that its imprint has survived several gigayears since the clusters formed.

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Figure 1: Projected stellar-spin inclinations of the 48 red giants of NGC 6791 and NGC 6819.
Figure 2: Spatial positions of the 48 red giants of NGC 6791 and NGC 6819.
Figure 3: Projected stellar-spin inclinations and proto-cluster formation from hydrodynamical simulations.


  1. 1

    Lee, E. J., Murray, N. & Rahman, M. Milky Way star-forming complexes and the turbulent motion of the galaxy’s molecular gas. Astrophys. J. 752, 146–159 (2012).

    Google Scholar 

  2. 2

    Longmore, S. N. et al. Protostars and Planets (eds. Beuther, H., Klessen, R., Dullemond, C. & Henning, T. ) Ch. 13, 291 (Univ. Arizona Press, 2014).

    Google Scholar 

  3. 3

    Lada, C. J. & Lada, E. A. Embedded clusters in molecular clouds. Ann. Rev. Astron. Astrophys. 41, 57–115 (2003).

    Google Scholar 

  4. 4

    McKee, C. F. & Ostriker, E. C. Theory of star formation. Ann. Rev. Astron. Astrophys. 45, 565–687 (2007).

    Google Scholar 

  5. 5

    Jackson, R. J. & Jeffries, R. D. Are the spin axes of stars randomly aligned within a cluster? Mon. Not. R. Astron. Soc. 402, 1380–1390 (2010).

    Google Scholar 

  6. 6

    Gizon, L. & Solanki, S. K. Determining the inclination of the rotation axis of a sun-like star. Astrophys. J. 589, 1009–1019 (2003).

    Google Scholar 

  7. 7

    Beck, P. G. et al. Fast core rotation in red-giant stars as revealed by gravity-dominated mixed modes. Nature 481, 55–57 (2012).

    Google Scholar 

  8. 8

    Huber, D. et al. Stellar spin-orbit misalignment in a multiplanet system. Science 342, 331 (2013).

    Google Scholar 

  9. 9

    Urquhart, J. S. et al. ATLASGAL—towards a complete sample of massive star forming clumps. Mon. Not. R. Astron. Soc. 443, 1555–1586 (2014).

    Google Scholar 

  10. 10

    Ballot, J., García, R. A. & Lambert, P. Rotation speed and stellar axis inclination from p modes: how CoRoT would see other suns. Mon. Not. R. Astron. Soc. 369, 1281–1286 (2006).

    Google Scholar 

  11. 11

    Benomar, O. et al. Nearly uniform internal rotation of solar-like main-sequence stars revealed by space-based asteroseismology and spectroscopic measurements. Mon. Not. R. Astron. Soc. 452, 2654–2674 (2015).

    Google Scholar 

  12. 12

    Bedding, T. R. et al. Gravity modes as a way to distinguish between hydrogen- and helium-burning red giant stars. Nature 471, 608–611 (2011).

    Google Scholar 

  13. 13

    Aerts, C., Christensen-Dalsgaard, J. & Kurtz, D. W. Asteroseismology Ch. 3 (Springer, 2010).

    Google Scholar 

  14. 14

    Basu, S. et al. Sounding open clusters: asteroseismic constraints from Kepler on the properties of NGC 6791 and NGC 6819. Astrophys. J. 729, L10–L15 (2011).

    Google Scholar 

  15. 15

    Stello, D. et al. An asteroseismic membership study of the red giants in three open clusters observed by Kepler: NGC 6791, NGC 6819, and NGC 6811. Astrophys. J. 739, 13–25 (2011).

    Google Scholar 

  16. 16

    Corsaro, E. et al. Asteroseismology of the open clusters NGC 6791, NGC 6811, and NGC 6819 from 19 months of Kepler photometry Astrophys. J. 757, 190–202 (2012).

    Google Scholar 

  17. 17

    Brogaard, K. et al. Age and helium content of the open cluster NGC 6791 from multiple eclipsing binary members. II. Age dependencies and new insights. Astron. Astrophys. 543, A106–A122 (2012).

    Google Scholar 

  18. 18

    Corsaro, E. & De Ridder, J. DIAMONDS: a new Bayesian nested sampling tool. Application to peak bagging of solar-like oscillations. Astron. Astrophys. 571, A71–A92 (2014).

    Google Scholar 

  19. 19

    Corsaro, E., De Ridder, J. & García, R. A. Bayesian peak bagging analysis of 19 low-mass low-luminosity red giants observed with Kepler. Astron. Astrophys. 579, A83–A158 (2015).

    Google Scholar 

  20. 20

    Meibom, S. et al. A spin-down clock for cool stars from observations of the 2.5-billion-year-old cluster. Nature 517, 589–591 (2015).

    Google Scholar 

  21. 21

    Geller, A. M., Hurley, J. R. & Mathieu, R. D. Direct N-body modeling of the old open cluster NGC 188: a detailed comparison of theoretical and observed binary star and blue straggler populations. Astron. J. 145, 8–29 (2013).

    Google Scholar 

  22. 22

    Hut, P. Tidal evolution in close binary systems. Astron. Astrophys. 99, 126–140 (1981).

    Google Scholar 

  23. 23

    Van den Bergh, S. & McClure, R. D. Galactic distribution of the oldest open clusters. Astron. Astrophys. 88, 360–362 (1980).

    Google Scholar 

  24. 24

    Lee, Y.-N. & Hennebelle, P. Formation of a protocluster: a virialized structure from gravoturbulent collapse. I. Simulation of cluster formation in a collapsing molecular cloud. Astron. Astrophys. 591, A30–A46 (2016).

    Google Scholar 

  25. 25

    Platais, I. A. et al. A new look at the old star cluster NGC 6791. Astrophys. J. 733, L1–L5 (2011).

    Google Scholar 

  26. 26

    Kalirai, J. S. et al. The CFHT open star cluster survey. II. Deep CCD photometry of the old open star cluster NGC 6819. Astron. J. 122, 266–282 (2001).

    Google Scholar 

  27. 27

    Brewer, L. N. et al. Determining the age of the Kepler open cluster NGC 6819 with a new triple system and other eclipsing binary stars. Astron. J. 151, 66–85 (2016).

    Google Scholar 

  28. 28

    Miglio, A. et al. Asteroseismology of old open clusters with Kepler: direct estimate of the integrated red giant branch mass-loss in NGC 6791 and 6819. Mon. Not. R. Astron. Soc. 419, 2007–2088 (2012).

    Google Scholar 

  29. 29

    Milliman, K. E. et al. WIYN open cluster study. LX. Spectroscopic binary orbits in NGC 6819. Astron. J. 148, 38–57 (2014).

    Google Scholar 

  30. 30

    Mosser, B. et al. Probing the core structure and evolution of red giants using gravity-dominated mixed modes observed with Kepler. Astron. Astrophys. 540, A143–A153 (2012).

    Google Scholar 

  31. 31

    Mosser, B. et al. Mixed modes in red giants: a window on stellar evolution. Astron. Astrophys. 572, L5–L9 (2014).

    Google Scholar 

  32. 32

    García, R. A. et al. Preparation of Kepler light curves for asteroseismic analyses. Mon. Not. R. Astron. Soc. 414, L6–L10 (2011).

    Google Scholar 

  33. 33

    García, R. A. et al. Impact on asteroseismic analyses of regular gaps in Kepler data. Astron. Astrophys. 568, A10–A18 (2014).

    Google Scholar 

  34. 34

    Pires, S. et al. Gap interpolation by inpainting methods: application to ground and space-based asteroseismic data. Astron. Astrophys. 574, A18–A27 (2014).

    Google Scholar 

  35. 35

    Vrard, M., Mosser, B. & Samadi, R. Period spacings in red giants. II. Automated measurement. Astron. Astrophys. 588, 87–99 (2016).

    Google Scholar 

  36. 36

    Mathur, S. et al. Revised stellar properties of Kepler targets for the Q1-17 (DR25) transit detection run. Preprint at (2016).

  37. 37

    Kallinger, T. et al. The connection between stellar granulation and oscillation as seen by the Kepler mission. Astron. Astrophys. 570, A41–A57 (2014).

    Google Scholar 

  38. 38

    Mathur, S. et al. Determining global parameters of the oscillations of solar-like stars. Astron. Astrophys. 511, A46–A58 (2010).

    Google Scholar 

  39. 39

    Tassoul, M. Asymptotic approximations for stellar nonradial pulsations. Astrophys. J. Suppl. Ser. 43, 469–490 (1980).

    Google Scholar 

  40. 40

    Buysschaert, B. et al. Testing the asymptotic relation for period spacings from mixed modes of red giants observed with the Kepler mission. Astron. Astrophys. 588, A82–A95 (2016).

    Google Scholar 

  41. 41

    Teyssier, R. Cosmological hydrodynamics with adaptive mesh refinement: a new high resolution code called RAMSES. Astron. Astrophys. 385, 337–364 (2002).

    Google Scholar 

  42. 42

    Fromang, S., Hennebelle, P. & Teyssier, R. A high order Godunov scheme with constrained transport and adaptive mesh refinement for astrophysical magnetohydrodynamics. Astron. Astrophys. 457, 371–384 (2006).

    Google Scholar 

  43. 43

    García, R. A. et al. Measuring reliable surface rotation rates from Kepler photometric observations. Astron. Soc. Pac. 479, 129–136 (2013).

    Google Scholar 

  44. 44

    McQuillan, A., Mazeh, T. & Aigrain, S. Rotation periods of 34,030 Kepler main-sequence stars: the full autocorrelation sample. Astrophys. J. Suppl. Ser. 211, 24–37 (2014).

    Google Scholar 

  45. 45

    García, R. A. et al. Rotation and magnetism of Kepler pulsating solar-like stars: towards asteroseismically calibrated age-rotation relations. Astron. Astrophys. 572, 34–48 (2014).

    Google Scholar 

  46. 46

    Ceillier, T. et al. Rotation periods and seismic ages of KOIs—comparison with stars without detected planets from Kepler observations. Mon. Not. R. Astron. Soc. 456, 119–125 (2016).

    Google Scholar 

  47. 47

    Aigrain, S. et al. Testing the recovery of stellar rotation signals from Kepler light curves using a blind hare-and-hounds exercise. Mon. Not. R. Astron. Soc. 450, 3211–3226 (2015).

    Google Scholar 

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E.C. is funded by the European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 312844 (SPACEINN) and by the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 664931. Y.-N.L. and P.H. acknowledge funding by the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007-2013 grant agreement no. 306483) and the HPC resources of CINES under the allocation x2014047023 made by GENCI (Grand Equipement National de Calcul Intensif). R.A.G. received funding from the CNES GOLF and PLATO grants at CEA. R.A.G. and P.G.B. received funding from the ANR (Agence Nationale de la Recherche, France) program IDEE (no. ANR-12-BS05-0008) ‘Interaction Des Étoiles et des Exoplanètes’. S.Mathur acknowledges support from the NASA grant NNX12AE17G. S.Mathis acknowledges funding by the European Research Council through ERC grant SPIRE no. 647383. D.S. is the recipient of an Australian Research Council Future Fellowship (project no. FT140100147). J.B. acknowledges financial support from grant ANR 2011 Blanc SIMI5-6 020 ‘Toupies: Towards understanding the spin evolution of stars’. This work has received funding from the CNES grants at CEA. All the light curves used in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts. UKIRT is supported by NASA and operated under an agreement among the University of Hawaii, the University of Arizona and Lockheed Martin Advanced Technology Center; operations are enabled through the cooperation of the East Asian Observatory. We thank D. Salabert for the preparation of the website containing the source data used in this work.

Author information




E.C. performed the fits of the background in the power spectra, identified the oscillation modes, measured the mode parameters and the inclination angles for all the stars in the sample, and interpreted the results. Y.-N.L. performed the hydrodynamical simulations of the proto-cluster formation and for the significance of the stellar-spin alignment, and contributed to interpreting the initial conditions in the molecular cloud. R.A.G. prepared the data sets calibrated for the asteroseismic analysis, contributed to discussing the analysis method and the observational results, and reanalysed the independent sample of stars observed in NGC 6819. P.H. contributed to the computation of the hydrodynamical simulations and in the interpretation of observational results and of the initial conditions in the molecular cloud. S.Mathur provided input guesses for the background properties in the power spectra of all the stars and contributed to the selection of the control sample. P.G.B. contributed to discussing the data analysis method and the identification of the oscillation modes. S.Mathis contributed to discussing the N-body interactions among stars in open clusters and to quantifying the tidal effects in binary stars. D.S. provided spatial positions for the entire population of red giants identified in the field of the two clusters and contributed to discussing the observational results and the data analysis method. J.B. provided theoretical and observational insights on the effect and evolution of angular momentum in stellar clusters. All authors commented on the manuscript.

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Correspondence to Enrico Corsaro.

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The authors declare no competing financial interests.

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Supplementary Figures 1–3 and Supplementary Tables 1–5. (PDF 536 kb)

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Corsaro, E., Lee, YN., García, R. et al. Spin alignment of stars in old open clusters. Nat Astron 1, 0064 (2017).

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