Stars, in general, have a spherical or roughly spherical shape. The force of gravity acting on the matter within a star causes it to collapse under its own weight, resulting in a shape that is balanced by the internal pressure from nuclear fusion reactions occurring in its core. This gravitational pressure and the outward pressure from the nuclear fusion process create a stable, spherical equilibrium.
However, it's important to note that stars are not perfectly smooth or solid objects. They consist of a superheated plasma composed of hydrogen, helium, and trace amounts of other elements. Within a star, various processes like convection, turbulence, and magnetic fields can influence the distribution of matter, leading to irregularities and dynamic structures such as sunspots, flares, and coronal loops.
Additionally, certain types of stars can exhibit non-spherical shapes due to factors such as rotation. Rapidly spinning stars can become flattened at the poles and bulge at the equator due to centrifugal forces. These stars are known as oblate spheroids or ellipsoids. However, it's important to note that even in these cases, the overall shape is still relatively close to a sphere.
In summary, while stars are generally considered to have a spherical shape, various factors and processes can introduce irregularities and deviations from a perfect sphere.