Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Identification of the long stellar stream of the prototypical massive globular cluster ω Centauri


Omega Centauri (ω Cen) is the Milky Way’s most massive globular cluster, and has long been suspected of being the remnant core of an accreted dwarf galaxy. If this scenario is correct, ω Cen should be tidally limited and tidal debris should be spread along its orbit. Here we use N-body simulations to show that the recently discovered ‘Fimbulthul’ structure is the long-sought-for tidal stream of ω Cen, extending up to 28° from the cluster. Follow-up high-resolution spectroscopy of five stream stars shows that they are closely grouped in velocity, and have metallicities consistent with having originated in that cluster. Informed by our N-body simulations, we devise a selection filter that we apply to Gaia mission data to also uncover the stream in the highly contaminated and crowded field within 10° of ω Cen. Further modelling of the stream may help to constrain the dynamical history of the dwarf galaxy progenitor of this disrupting system and guide future searches for its remnant stars in the Milky Way.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Physical properties of the Fimbulthul stream as a function of \(\ell\).
Fig. 2: Present-day configuration of an N-body simulation of the disruption of a massive globular cluster on the orbit of ω Cen.
Fig. 3: Comparison of the colour-magnitude diagram of ω Cen and Fimbulthul in the Gaia photometric system.
Fig. 4: Stars with kinematic properties of the expected stream near ω Cen, fulfilling colour and magnitude selection criteria.

Data availability

The Gaia DR2 data on which this study was based are available at The Fimbulthul stars shown in Fig. 1 are listed in Supplementary Table 1.


  1. 1.

    Harris, W. E. A catalog of parameters for globular clusters in the Milky Way. Astron. J. 112, 1487–1488 (1996).

    ADS  Article  Google Scholar 

  2. 2.

    Johnson, C. I. & Pilachowski, C. A. Chemical abundances for 855 giants in the globular cluster Omega Centauri (NGC 5139). Astrophys. J. 722, 1373–1410 (2010).

    ADS  Article  Google Scholar 

  3. 3.

    Bellini, A. et al. The HST large programme on Omega Centauri. II. Internal kinematics. Astrophys. J. 853, 86 (2018).

    ADS  Article  Google Scholar 

  4. 4.

    Marino, A. F. et al. The C+N+O abundance of Omega Centauri giant stars: implications for the chemical-enrichment scenario and the relative ages of different stellar populations. Astrophys. J. 746, 14 (2012).

    ADS  Article  Google Scholar 

  5. 5.

    Zinnecker, H., Keable, C. J., Dunlop, J. S., Cannon, R. D. & Griffiths, W. K. In The Harlow Shapley Symposium on Globular Cluster Systems in Galaxies (eds Grindlay, J. E. & Davis Philip, A. G.) 603–604 (IAU, 1988).

  6. 6.

    Majewski, S. R. et al. In Proc. 35th Liege International Astrophysical Colloquia, The Galactic Halo: From Globular Cluster to Field Stars (eds Noels, A. et al.) 619–622 (Institut d’Astrophysique et de Geophysique, 2000).

  7. 7.

    Bekki, K. & Freeman, K. C. Formation of Omega Centauri from an ancient nucleated dwarf galaxy in the young Galactic Disc. Mon. Not. R. Astron. Soc. 346, L11–L15 (2003).

    ADS  Article  Google Scholar 

  8. 8.

    Mizutani, A., Chiba, M. & Sakamoto, T. Kinematics of tidal debris from Omega Centauri’s progenitor galaxy. Astrophys. J. 589, L89–L92 (2003).

    ADS  Article  Google Scholar 

  9. 9.

    Ideta, M. & Makino, J. Formation of Omega Centauri by tidal stripping of a dwarf galaxy. Astrophys. J. 616, L107–L110 (2004).

    ADS  Article  Google Scholar 

  10. 10.

    Tsuchiya, T., Korchagin, V. I. & Dinescu, D. I. Disruption of a dwarf galaxy under strong shocking: the origin of Omega Centauri. Mon. Not. R. Astron. Soc. 350, 1141–1151 (2004).

    ADS  Article  Google Scholar 

  11. 11.

    Johnston, K. V., Hernquist, L. & Bolte, M. Fossil signatures of ancient accretion events in the halo. Astrophys. J. 465, 278–287 (1996).

    ADS  Article  Google Scholar 

  12. 12.

    Johnston, K. V., Zhao, H., Spergel, D. N. & Hernquist, L. Tidal streams as probes of the Galactic potential. Astrophys. J. 512, L109–L112 (1999).

    ADS  Article  Google Scholar 

  13. 13.

    Ibata, R., Lewis, G. F., Irwin, M., Totten, E. & Quinn, T. Great circle tidal streams: evidence for a nearly spherical massive dark halo around the Milky Way. Astrophys. J. 551, 294–311 (2001).

    ADS  Article  Google Scholar 

  14. 14.

    Law, D. R. & Majewski, S. R. The Sagittarius dwarf galaxy: a model for evolution in a triaxial Milky Way halo. Astrophys. J. 714, 229–254 (2010).

    ADS  Article  Google Scholar 

  15. 15.

    Küpper, A. H. W. et al. Globular cluster streams as Galactic high-precision scales—the poster child palomar 5. Astrophys. J. 803, 80 (2015).

    ADS  Article  Google Scholar 

  16. 16.

    Ibata, R. A., Lewis, G. F., Irwin, M. J. & Quinn, T. Uncovering cold dark matter halo substructure with tidal streams. Mon. Not. R. Astron. Soc. 332, 915–920 (2002).

    ADS  Article  Google Scholar 

  17. 17.

    Johnston, K. V., Spergel, D. N. & Haydn, C. How lumpy is the Milky Way’s dark matter halo? Astrophys. J. 570, 656–664 (2002).

    ADS  Article  Google Scholar 

  18. 18.

    Carlberg, R. G. Dark matter sub-halo counts via star stream crossings. Astrophys. J. 748, 20 (2012).

    ADS  Article  Google Scholar 

  19. 19.

    Erkal, D., Belokurov, V., Bovy, J. & Sanders, J. L. The number and size of subhalo-induced gaps in stellar streams. Mon. Not. R. Astron. Soc. 463, 102–119 (2016).

    ADS  Article  Google Scholar 

  20. 20.

    Gaia Collaboration Gaia data release 2. Summary of the contents and survey properties. Astron. Astrophys. 616, A1 (2018).

    Article  Google Scholar 

  21. 21.

    Gaia Collaboration Gaia data release 2. The astrometric solution. Astron. Astrophys. 616, A2 (2018).

    Article  Google Scholar 

  22. 22.

    Ibata, R., Malhan, K. & Martin, N. The streams of the gaping abyss: a population of entangled stellar streams surrounding the inner galaxy. Astrophys. J. 872, 152 (2019).

    ADS  Article  Google Scholar 

  23. 23.

    Malhan, K. & Ibata, R. A. STREAMFINDER—I. A new algorithm for detecting stellar streams. Mon. Not. R. Astron. Soc. 477, 4063–4076 (2018).

    ADS  Article  Google Scholar 

  24. 24.

    Bressan, A. et al. PARSEC: stellar tracks and isochrones with the PAdova and TRieste stellar evolution code. Mon. Not. R. Astron. Soc. 427, 127–145 (2012).

    ADS  Article  Google Scholar 

  25. 25.

    Malhan, K., Ibata, R. A. & Martin, N. F. Ghostly tributaries to the Milky Way: charting the halo’s stellar streams with the Gaia DR2 catalogue. Mon. Not. R. Astron. Soc. 481, 3442–3455 (2018).

    ADS  Article  Google Scholar 

  26. 26.

    Ibata, R. A., Malhan, K., Martin, N. F. & Starkenburg, E. Phlegethon, a nearby 75 degree-long retrograde stellar stream. Astrophys. J. 865, 85 (2018).

    ADS  Article  Google Scholar 

  27. 27.

    Gaia Collaboration Gaia data release 2. Kinematics of globular clusters and dwarf galaxies around the Milky Way. Astron. Astrophys. 616, A12 (2018).

    Article  Google Scholar 

  28. 28.

    Bianchini, P., Varri, A. L., Bertin, G. & Zocchi, A. Rotating globular clusters. Astrophys. J. 772, 67 (2013).

    ADS  Article  Google Scholar 

  29. 29.

    Braga, V. F. et al. On the RR Lyrae stars in globulars. V. The complete near-infrared (JHKs) census of Omega Centauri RR Lyrae variables. Astron. J. 155, 137 (2018).

    ADS  Article  Google Scholar 

  30. 30.

    Fernandez-Trincado, J. G. et al. RAVE stars tidally stripped or ejected from the Omega Centauri globular cluster. Astron. Astrophys. 583, A76 (2015).

    Article  Google Scholar 

  31. 31.

    Gilmore, G., Wyse, R. F. G. & Norris, J. E. Deciphering the last major invasion of the Milky Way. Astrophys. J. 574, L39–L42 (2002).

    ADS  Article  Google Scholar 

  32. 32.

    Meza, A., Navarro, J. F., Abadi, M. G. & Steinmetz, M. Accretion relics in the solar neighbourhood: debris from omega Cen’s parent galaxy. Mon. Not. R. Astron. Soc. 359, 93–103 (2005).

    ADS  Article  Google Scholar 

  33. 33.

    Altmann, M., Catelan, M. & Zoccali, M. Searching for merger debris in the Galactic halo: chemodynamical evidence based on local blue HB stars. Astron. Astrophys. 439, L5–L8 (2005).

    ADS  Article  Google Scholar 

  34. 34.

    Majewski, S. R. et al. Exploring halo substructure with giant stars: substructure in the local halo as seen in the grid giant star survey including extended tidal debris from Omega Centauri. Astrophys. J. 747, L37 (2012).

    ADS  Article  Google Scholar 

  35. 35.

    Helmi, A., Veljanoski, J., Breddels, M. A., Tian, H. & Sales, L. V. A box full of chocolates: the rich structure of the nearby stellar halo revealed by Gaia and RAVE. Astron. Astrophys. 598, A58 (2017).

    ADS  Article  Google Scholar 

  36. 36.

    Koppelman, H., Helmi, A. & Veljanoski, J. One large blob and many streams frosting the nearby stellar halo in Gaia DR2. Astrophys. J. 860, L11 (2018).

    ADS  Article  Google Scholar 

  37. 37.

    Myeong, G. C., Evans, N. W., Belokurov, V., Sanders, J. L. & Koposov, S. E. Discovery of new retrograde substructures: the shards of Omega Centauri? Mon. Not. R. Astron. Soc. 478, 5449–5459 (2018).

    ADS  Article  Google Scholar 

  38. 38.

    Leon, S., Meylan, G. & Combes, F. Tidal tails around 20 Galactic globular clusters. Observational evidence for gravitational disk/bulge shocking. Astron. Astrophys. 359, 907–931 (2000).

    ADS  Google Scholar 

  39. 39.

    Donati, J. F., Semel, M., Carter, B. D., Rees, D. E. & Collier Cameron, A. Spectropolarimetric observations of active stars. Mon. Not. R. Astron. Soc. 291, 658–682 (1997).

    ADS  Article  Google Scholar 

  40. 40.

    Starkenburg, E. et al. The NIR Ca ii triplet at low metallicity. Searching for extremely low-metallicity stars in classical dwarf galaxies. Astron. Astrophys. 513, 34 (2010).

    Article  Google Scholar 

  41. 41.

    Gratton, R. G. The absolute magnitude of field metal-poor horizontal branch stars. Mon. Not. R. Astron. Soc. 296, 739–745 (1998).

    ADS  Article  Google Scholar 

  42. 42.

    Jordi, C. et al. Gaia broad band photometry. Astron. Astrophys. 523, A48 (2010).

    Article  Google Scholar 

  43. 43.

    Teuben, P. The stellar dynamics toolbox NEMO. In ASP Conf. Ser. 77, Astronomical Data Analysis Software and Systems IV (eds Shaw, R. A., Payne, H. E. & Hayes, J. J. E.) 398–401 (ASP, 1995).

  44. 44.

    Dehnen, W. & Binney, J. Mass models of the Milky Way. Mon. Not. R. Astron. Soc. 294, 429–438 (1998).

    ADS  Article  Google Scholar 

  45. 45.

    Gravity Collaboration Detection of the gravitational redshift in the orbit of the star S2 near the Galactic Centre massive black hole. Astron. Astrophys. 615, L15 (2018).

    ADS  Article  Google Scholar 

  46. 46.

    Karim, M. T. & Mamajek, E. E. Revised geometric estimates of the north Galactic pole and the Sun’s height above the Galactic mid-plane. Mon. Not. R. Astron. Soc. 465, 472–481 (2017).

    ADS  Article  Google Scholar 

  47. 47.

    Schönrich, R., Binney, J. & Dehnen, W. Local kinematics and the local standard of rest. Mon. Not. R. Astron. Soc. 403, 1829–1833 (2010).

    ADS  Article  Google Scholar 

  48. 48.

    Varri, A. L. & Bertin, G. Self-consistent models of quasi-relaxed rotating stellar systems. Astron. Astrophys. 540, A94 (2012).

    ADS  Article  Google Scholar 

  49. 49.

    Bianchini, P. et al. The internal rotation of globular clusters revealed by Gaia DR2. Mon. Not. R. Astron. Soc. 481, 2125–2139 (2018).

    ADS  Article  Google Scholar 

  50. 50.

    Dehnen, W. A hierarchical O(N) force calculation algorithm. J. Comput. Phys. 179, 27–42 (2002).

    ADS  MathSciNet  Article  Google Scholar 

  51. 51.

    Gratton, R. G., Johnson, C. I., Lucatello, S., D’Orazi, V. & Pilachowski, C. Multiple populations in Omega Centauri: a cluster analysis of spectroscopic data. Astron. Astrophys. 534, A72 (2011).

    ADS  Article  Google Scholar 

Download references


This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. We thank the staff of the CFHT for taking the ESPaDOnS data used here, and for their continued support throughout the project. Based on observations obtained at the CFHT, which is operated by the National Research Council of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientique of France and the University of Hawaii. This work has been published under the framework of the IdEx Unistra and benefits from a funding from the state managed by the French National Research Agency as part of the investments for the future programme. PyRAF is a product of the Space Telescope Science Institute, which is operated by AURA for NASA. R.A.I. and N.M. gratefully acknowledge support from a ‘Programme National Cosmologie et Galaxies’ grant.

Author information




All authors assisted in the development, analysis and writing of the paper. R.A.I., K.M. and N.M. devised the STREAMFINDER software that detected the Fimbulthul stream. M.B. analysed the Gaia mission data to reveal the presence of the stream close to ω Cen. The spectroscopic measurements were performed by R.A.I. The initial conditions for the dynamical model of ω Cen were developed by P.B.

Corresponding author

Correspondence to Rodrigo A. Ibata.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Table 1

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Ibata, R.A., Bellazzini, M., Malhan, K. et al. Identification of the long stellar stream of the prototypical massive globular cluster ω Centauri. Nat Astron 3, 667–672 (2019).

Download citation

Further reading


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing