Radio continuum is from hot, electrically charged gas. Atomic hydrogen emission comes from warm gas. Molecular hydrogen lies in cold clouds, where stars form. Visible light is mostly from sunlike stars. Ultraviolet is heavily obscured by interstellar junk.
X rays come from energized gas.
Gamma rays appear where high-speed subatomic particles collide with interstellar hydrogen. The prominent mass of agitated gas, known as Sagittarius A, marks the exact hub of our galaxy and may contain a massive black hole. Just above and to the left are nebulae full of hot, newborn stars. Round puffs are the remnants of supernova explosions that spew out oxygen, carbon, and nitrogen the chemicals of life. The whole picture is about four degrees wide, or eight times the width of the full moon.