Planetary Nebula Nebula formed by the ejection of the outer shell of a star. Called planetary because of the disk like appearance in small telescopes. Newtonian A type of telescope using a front surfaced parabolic mirror to collect light and bring to a focal point for examination by the observer. Named after Sir Isaac Newton the British theorist. The NGC was inspired by and built on the observations of the Herschels.
Open clusters are relatively young stars and are almost always found along the Milky Way.
The youngest open cluster are still shrouded by the remnants of the gas out of which they were formed. Globular Clusters are characterized by a densely packed circular grouping of stars. They are among the oldest objects found in galaxies. Globulars orbit the parent galaxy forming a galactic halo. A single globular cluster may contain over 100,000 stars.