The sizes of a neutron star and a quark star compared to the Grand Canyon. The smallest, most massive, most compressed neutron star possible is about 17 kilometers in diameter. A quark star can be smaller than 11 kilometers diameter. The canyon is 29 kilometers from rim to rim. In reality this scene couldn't exist; the entire Earth would collapse almost instantly to a thin layer coating the surface of either superdense star. Illustration by D. Berry / Chandra X-ray Center.
Neutron stars tend to lie in the range of 1.4 to 2 solar masses. Any star with a neutron star’s density that’s over 10 solar masses has to become a black hole. That leaves a bit of a gap, although there is evidence of stellar black holes down to only 3 solar masses. The theoretical gap for strange stars to form may only be in the 2 to 3 solar masses range.