exploring a spiral galaxy's swirling dust and stars

spiral galaxy stars dust space cosmos universe astronomy nebula celestial night sky deep cosmic star formation galactic structure arms interstellar medium stellar evolution light years astronomical object core pattern wonder exploration travel scientific discovery cosmology astrophysics dynamics center clusters gas supernova remnants dark matter black hole gravitational forces rays radiation electromagnetic wavelengths spectral lines redshift blueshift hubble 039 law expanding big bang theory observable extragalactic