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.

  • Brief Communications Arising
  • Published:


Quark matter in compact stars?


Arising from: F. Özel. Nature 441, 1115–1117 (2006)10.1038/nature04858; Özel replies

In a theoretical interpretation of observational data from the neutron star EXO 0748–676, Özel concludes that quark matter probably does not exist in the centre of neutron stars1. However, this conclusion is based on a limited set of possible equations of state for quark matter. Here we compare Özel's observational limits with predictions based on a more comprehensive set of proposed quark-matter equations of state from the literature, and conclude that the presence of quark matter in EXO 0748–676 is not ruled out.

This is a preview of subscription content, access via your institution

Access options

Buy this article

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Lower limit of mass, M, and radius, R, from Özel's analysis of EXO 0748–676 (1σ and 2σ error bars are shown), and the calculated MR curve for various quark- and nuclear-matter equations of state.

Similar content being viewed by others


  1. Özel, F. Nature 441, 1115–1117 (2006).

    Article  ADS  Google Scholar 

  2. Alford, M., Braby, M., Paris, M. & Reddy, S. Astrophys. J. 629, 969–978 (2005).

    Article  ADS  Google Scholar 

  3. Fraga, E. S., Pisarski, R. D. & Schaffner-Bielich, J. Phys. Rev. D 63, 121702 (2001).

    Article  ADS  Google Scholar 

  4. Rüster, S. B. & Rischke, D. H. Phys. Rev. D 69, 045011 (2004).

    Article  ADS  Google Scholar 

  5. Page, D., Geppert, U. & Weber, F. Nucl. Phys. A 777, 497–530 (2006).

    Article  ADS  Google Scholar 

  6. Klähn, T. et al. Phys. Rev. C 74, 035802 (2006).

    Article  ADS  Google Scholar 

  7. Grigorian, H., Blaschke, D. & Voskresensky, D. Phys. Rev. C 71, 045801 (2005).

    Article  ADS  Google Scholar 

  8. Klahn, T. et al. arXiv:nucl-th/0609067 (2006).

  9. Madsen, J. Phys. Rev. Lett. 85, 10–13 (2000).

    Article  ADS  CAS  Google Scholar 

  10. Link, B. Phys. Rev. Lett. 91, 101101 (2003).

    Article  ADS  Google Scholar 

  11. Alpar, M. A. Phys. Rev. Lett. 58, 2152 (1987).

    Article  ADS  CAS  Google Scholar 

  12. Alford, M., Rajagopal, K. & Wilczek, F. Nucl. Phys. B 537, 443–458 (1999).

    Article  ADS  Google Scholar 

  13. Alford, M., Bowers, J. A. & Rajagopal, K. Phys. Rev. D 63, 074016 (2001).

    Article  ADS  Google Scholar 

  14. Watts, A. L. & Reddy, S. arXiv:astro-ph/0609364 (2006).

  15. Page, D. & Cumming, A. Astrophys. J. Lett. 635, L157–L160 (2005).

    Article  ADS  CAS  Google Scholar 

Download references

Author information

Authors and Affiliations


Rights and permissions

Reprints and permissions

About this article

Cite this article

Alford, M., Blaschke, D., Drago, A. et al. Quark matter in compact stars?. Nature 445, E7–E8 (2007).

Download citation

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


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