Horsehead Nebula, (catalog number IC 434), ionized-hydrogen region in the constellation Orion. The nebula consists of a cloud of ionized gas lit from within by young, hot stars; a dark cloud containing interstellar dust lies immediately in front. The dus
Orion Nebula (M42)Centre of the Orion Nebula (M42). Astronomers have identified some 700 young stars in this 2.5-light-year-wide area. They have also detected over 150 protoplanetary disks, or proplyds, which are believed to be embryonic solar systems that will eventually form planets. These ...