Stellar Life Cycle in Giant Galactic Nebula NGC 3603

NGC 3603 is a giant HII region in the Carina spiral arm of the southern Milky Way, some 20,000 light years (6 kpc) away from our solar system. HII stands for ionized hydrogen. Gas clouds consist predominantly of hydrogen, the lightest and most abundant element in the universe. When exposed to ultraviolet radiation from hot stars the gas becomes ionized. Hydrogen atoms are stripped of their only electron, and the proton remains. While hydrogen atoms become ionized, ions recombine with free electrons to form again neutral atoms. When recombining the electrons emit light at characteristic wavelengths. NGC 3603 is actually only a dwarf among giant HII regions - there are other galaxies with much larger regions of this kind. But NGC 3603 is the closest giant HII region and the best resolved one. In fact it is the only giant HII region in our Galaxy that is visible at optical wavelengths. NGC 3603 has been the subject of many studies from the ground and space, but the high resolution of recent Hubble Space Telescope observations revealed a number of previously unknown features and nicely illustrates the complexity of this nearby starburst region.