What escape velocity would quark stars have? Quark stars are hypothetical compact stars that are denser than neutron stars and maybe the last stage of upholding matter before stars that collapse into a singularity. Neutron stars have escape velocities up to half the speed of light, and the escape velocity of quark stars must be even closer to c. Could it be that some or all black holes are quark stars whose escape velocity is just above 1 c, rather than singularities?
The escape velocity (in terms of Schwarzschild coordinates) from the surface of a quark star will be given by
$$ v = c\left(\frac{r_s}{r_q}\right)^{1/2}, $$
where $r_s$ is the Schwarzschild radius, $2GM/c^2$, and $r_q$ is the &quot;radius&quot; of the quark star. Strictly speaking, $2\pi r_q$ is the circumference of the quark star.
Since $r_s &lt; r_q$, this does not exceed the speed of light.
However, this applies to objects launched radially outwards. The escape velocity is higher at other angles. Not even light can escape if launched tangentially at $r = 1.5 r_s$ and quark stars could be smaller than this.
If the quark star is spinning (and it would be) the escape velocity becomes even more complex.