I was tempted to make some really horrid joke out of the thread title, but two people have already beat me to it. So:
A bit of a derail, but I haven't seen it discussed here: One of the major astrophysical enigmas is whether or not "quark" stars exist. These would be something intermediate to neutron stars and black holes, where the gravitational squeezing is enough to dissociate neutrons into their constituent quarks, but not enough to actually cause complete collapse into a black hole. From what I've read, physicists think there exists a set of boundary conditions in which this kind of object could exist, although it might be temporary, by astrophysical standards. A typical neutron star has the diameter of a large city. A quark star, would be about half that size. But, as opposed to neutron stars, which emit energy in the form of x-rays and some longer-wave radiation (including the visible spectrum), a quark star might emit nothing visible. So how would it be detected? The gravitational pull would be great, but concentrated in a very small space, and really difficult to discern, if it were even possible.
Damn them gluons, anyway.
caw