Lines at 500.7 nm, and 495.9 nm correspond to forbidden transitions in a doubly-ionized ion of this element, which are commonly found in planetary nebulae. Its not hydrogen, but the ratio of the abundance of this element to iron is larger than the sun's value in stars that have low metallicity, because type II supernovae produce this element more readily than iron. One iso
Lines at 500.7 nm, and 495.9 nm correspond to forbidden transitions in a doubly-ionized ion of this element, which are commonly found in planetary nebulae. Its not hydrogen, but the ratio of the abundance of this element to iron is larger than the sun's value in stars that have low metallicity, because type II supernovae produce this element more readily than iron. One isotope of this element has a half-life of 122.24 seconds and undergoes beta-plus decay to release 1.73 MeV of energy in a common fusion process. In massive stars, two atoms of this element fuse together to form silicon in this element's namesake burning process, which occurs after the (*) neon-burning process. White dwarves are usually composed of carbon and this element. This element is the third most abundant in both the solar system and the galaxy, and names a fusion cycle along with carbon and nitrogen. For 10 points, name this element which also comprises 21% of the Earth's atmosphere.
Lines at 500.7 nm, and 495.9 nm correspond to forbidden transitions in a doubly-ionized ion of this element, which are commonly found in planetary nebulae.
oxygen