Voyager probes detect Milky Way glow

National Geographic : The two Voyager spacecraft, first launched more than 30 years ago, have detected a type of UV radiation coming from the Milky Way that until now was rendered effectively invisible by the Sun’s radiation. Known as Lyman-alpha, the radiation arises when hydrogen’s lone electron hops down from the n = 2 quantum level to the n = 1 level. Regions rich in Lyman-alpha emission have been observed in other galaxies and associated with their stellar nurseries. Most of the emission that the Voyager probes have detected in our own galaxy also appears to emanate from star-forming regions. The new data may ultimately aid in the detection of the first appearance of stars in the universe.