In Newtonian mechanics, objects dense enough to trap any emitted light are called dark stars,[1][2][a], as opposed to black holes in general relativity.
It is expected to be smaller and denser than a neutron star, and may survive in this new state indefinitely, if no extra mass is added.
Based on observations released by the Chandra X-Ray Observatory on 10 April 2002, two objects, named RX J1856.5−3754 and 3C 58, were suggested as quark star candidates.
The former appeared to be much smaller and the latter much colder than expected for a neutron star, suggesting that they were composed of material denser than neutronium.
This proposed process might occur in a volume at the star's core approximately the size of an apple, containing about two Earth masses, and reaching temperatures on the order of 1015 K (1 PK).
However, current observations[7] from particle accelerators speak against the existence of preons, or at least do not prioritize their investigation, since the only particle detector presently able to explore very high energies (the Large Hadron Collider) is not designed specifically for this and its research program is directed towards other areas, such as studying the Higgs boson, quark–gluon plasma and evidence related to physics beyond the Standard Model.
The immense gravity of a compact boson star would bend light around the object, creating an empty region resembling the shadow of a black hole's event horizon.
[24] Braaten, Mohapatra, and Zhang have theorized that a new type dense axion-star may exist in which gravity is balanced by the mean-field pressure of the axion Bose–Einstein condensate.
Under these conditions, assuming gravity and spacetime are quantized, there arises a repulsive "force" derived from Heisenberg's uncertainty principle.