Nebulae are large clouds of gas in space. They are primarily composed of hydrogen gas, but they usually contain smaller amounts of other common gases and dust. Nebulae that glow only from reflected starlight are called reflection nebulae. Investigate the various varieties of nebulae using Wolfram|Alpha.
Explore emission nebulae, which glow due to the gases being excited by ultraviolet light from nearby stars.
Query for properties of H II regions, which are a type of emission nebula where active star formation is happening and the ionization comes from these newly formed stars.
Obtain data on planetary nebulae, which are a specific type of nebula resulting from the outer layers of a Sun-mass-sized star being thrown off as the star dies.