Globular clusters : Globular clusters are star clusters that have remained in a gravitationally bound system for a long time. These clusters are typically spherical in shape and can contain a few thousand to a million stars. Globular clusters are found in the spherical halo of our galaxy, so they are found above, below, and level with the plane of our flat, disk-shaped Milky Way. They are typically around 13 billion years old, containing some of the oldest stars in our galaxy. As a result, astronomers use them to learn more about our galaxy's early history and what the Milky Way was like when these stars formed.
3.Open cluster: Open clusters are significantly younger and smaller in size than globular clusters. They are the most recent birthplaces of new stars, which form from dust and gas clouds and contain only hundreds or thousands of stars. Though the stars in an open cluster formed from the same material, they do not remain gravitationally bound over time and scatter their stars far and wide. These clusters can have random and irregular shapes because they are not gravitationally bound. They are located in our galaxy's plane, along the spiral arms that contain the Milky Way's gas and dust. Open clusters are used by astronomers to study young stars and the processes of star formation, as well as the dynamics of how material spreads out in our galaxy, because they are both younger and shorter lived.
4. Emission nebula: An emission nebula is a nebula composed of clouds of ionized gases that emit light of various wavelengths.
5. Planetary nebula : A planetary nebula represents a stage of stellar evolution that the sun will go through in billions of years. When a star, such as the sun, exhausts all of the hydrogen in its core, it expands into a red giant, with a radius that grows by tens to hundreds of times. A star sheds most of its outer layers during this phase, eventually leaving behind a hot core that will soon contract to form a dense white dwarf star. A fast wind from the hot core rams into the ejected atmosphere, pushing it outward and creating the graceful, shell-like filamentary structures visible through optical telescopes.
6. Reflection nebula : A reflection nebula, like the fog around a street lamp, only shines when the light from an embedded source illuminates its dust; it does not produce any visible light on its own.
7. Dark nebula: Interstellar clouds called "dark nebula" have a lot of dust in them. They are entirely opaque at visible wavelengths as a result of being able to scatter and absorb all incident optical light. When they are situated in front of a bright emission nebula, as the Horsehead nebula in Orion, or in an area with a lot of stars, they are the most noticeable (e.g. Barnard 68 in Ophiuchus).
