Types of Telescopic Objects

Open Clusters:

Open clusters are groups of stars held together by mutual gravitational attraction. All Open Clusters are part of our Milky Way galaxy that supposedly originate from large cosmic gas/dust clouds. They are considered to be relatively young in cosmological terms, in the hundreds of millions of years.

Globular Clusters:

Globular clusters are concentrated, gravitationally bound ranging anywhere from ten thousand to one million stars. They populate the halo or bulge of the Milky Way and other galaxies with a significant concentration toward the Galactic Center. Spectroscopic study of globular clusters shows that they are much lower in heavy element abundance than stars such as the Sun that form in the disks of galaxies; elements that are essential for life to form. Thus, globular clusters are believed to be very old and formed from an earlier generation of stars (Population II).Recentestimates for age range from 12 to 20 billion years, not too much younger than the universe itself.

Galaxies:

Galaxies come in a variety of types and shapes. The most well known is the spiral type. Our own Milky way is a spiral galaxy. The famous Andromeda galaxy is our closest galactic neighbor and is a spiral as well. A lenticular galaxy is shaped like a spiral but does not have the defined spiral arms. Lenticular galaxies are very old, containing mostly Population II stars. Irregular galaxies are believed to have taken their observed shapes due to gravitational distortion. Elliptical galaxies are simply elliptical is shape and do not rotate.