Atoms occupy about 4% of the total energy density in the observed universe, with an average density of about 0.25 atom/m3.In the Milky Way galaxy, the atom has a higher concentration, with the density of matter in the interstellar medium ranged from 105 to 109 atom/m3.
The sun itself is believed to be in the Local Bubble, which is an area that many gas mengadung ions, so the surroundings are denistas approximately 103 atom/m3. Star forming dense clouds in the interstellar medium, and the evolutionary process of stars would lead to increased content of elements heavier than hydrogen and helium in the interstellar medium.
Up to 95% of atoms are concentrated in the Milky Way stars, and the total mass of these atoms form approximately 10% of the mass of galaxies. (The mass of the rest is dark matter that is not clearly known.
