Compact stars in the standard model - and beyond

In the context of the standard model of particle physics, there is a definite upper limit to the density of stable compact stars. However, if there is a deeper layer of constituents, below that of quarks and leptons, stability may be re-established far beyond this limiting density and a new class of compact stars could exist. These objects would cause gravitational lensing of gamma-ray bursts and white dwarfs, which might be observable as line features in the spectrum. Such observations could provide means for obtaining new clues about the fundamental particles and the nature of cold dark matter.