2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/7507After a brief introduction to the necessary of quark stars in modelling pulsars, I present a qualitative analysis of the solidification of quark matter with low-temperature but high-density. The reason, that a solid neutron star could not be possible, is also given.3 pages, no figure. Proceedings of CAS Symposium No.365/The 18th Guo Shoujing Summer School on Astrophysics: "Beyond the Milky Way: Progress in Extragalactic X-Ray Astronomy with Chandra and XMM-Newton" (September 21-24, 2003), Eds: Fuzhen Cheng, Junhan You, and K. MakishimaAstrophysicsHigh Energy Physics - Phenomenologytext