Astrophysics (Astro = star, physics = nature) is the science that explores physics on a greater scale, aiming to explain the nature of space. These include the physical properties of stellar objects such as neutron stars and black holes, the motion of extraterrestrial objects and the interstellar medium. An expansion of this is cosmology, which is theoretical astrophysics on a much larger scale.
Learn about Black hole, The Big Bang, Sting Theory and various other theories
