a close-up of a spiral galaxy with its bright core with stars and cosmic dust

spiral galaxy milky types structure arms galactic center bulge disc halo star formation nebulae interstellar medium dark matter cosmic dust stars constellations astronomy astrophysics universe cosmos deep space exploration supermassive black hole year lightyear redshift blueshift hubble constant microwave background radiation big bang energy cosmology extraterrestrial life exoplanet astrobiology nasa telescope observatory