We can study the swirling patterns of galaxies and nebulae, and learn a lot from this, as they evolve over time. Stars and gas clouds can be great fun to observe, because they are bright and showy, but there are far stranger objects in the sky. The largest singular solid objects in existence, in terms of their mass, are the collapsed cores of dead stars. Whether a star becomes a white dwarf, a neutron star, or a black hole upon expiring depends almost exclusively upon its mass prior to extinction. Larger stars are destined to become one of the latter.
Stars burn by evolving higher elements through nuclear fusion.
When a star has expended its primary fuel, hydrogen, it will at first begin to burn secondary sources of fuel, starting with helium. Each time it runs out of a source of fuel, it will implode, then heat up through gravitational compression, until the next heavier element will burn. As this process proceeds in a larger star, its outer atmosphere will puff up, and it will become a red giant. When a certain point is reached, no more energy can be derived from the available fuel, and the star collapses. It goes nova, flaring brightly for a relatively short while, then it winks out.