Astronomers use the principle of parallax to measure distances to the closer stars. Here, the term parallax is the semi-angle of inclination between two sight-lines to the star, as observed when the Earth is on opposite sides of the Sun in its orbit.
Ernest Rutherford discovered that atoms contain mostly empty space, with his gold foil experiment. Bhor discovered that the electrons are not randomly placed around the nucleu â¦ s.
Astronomers like to call all material made up of protons, neutrons and electrons baryonic matter. Until about thirty years ago, astronomers thought that the universe was composed almost entirely of this baryonic matter, ordinary atoms.