The name of our own galaxy in which the Sun resides. A cloud of interstellar gas and dust. Most Messier objects are included in these catalogs. Most open star clusters are moderately young with ages approximated by their main sequence stars of earliest spectral class . A type of emission nebula containing an expanding shell of gas surrounding very hot stars in a late stage of stellar evolution.
Planetary nebulae are of the emission type.
A type of nebula that is cool and shines because the dust within scatters the light from nearby or embedded stars. Hence, the cloud is not self luminous. A type of galaxy with spiral arms. A group of physically associated stars bound by gravitation and presumably having a common origin.