Population I stars
Global Cluster
a galaxy is a group of stars.
Stars come in a variety of types. Blue stars, which are very hot, tend to have shorter lifetimes than red stars, which are cooler. Regions of galaxies where stars are currently forming are therefore bluer than regions where there has been no recent star formation. Spiral galaxies seem to have a lot of gas and dust, while elliptical galaxies have very little gas or dust.
The concentration of stars is typically more centrally located in elliptical galaxies compared to spiral galaxies. Elliptical galaxies have a more concentrated spheroidal shape with stars distributed densely in the center, while spiral galaxies have a more spread-out disk structure with stars distributed along spiral arms.
The Milky Way is the galaxy in which our sun is located. The local group of stars is part of the Milky Way and therefore smaller than it is. The local Group of galaxies is a cluster of galaxies and therefore larger than the Milky Way.
We see the stars in the sky, from our perspective of being here on the Earth. Stars are grouped into galaxies of billions of stars, and there are vast almost-empty spaces between the galaxies.
Elliptical galaxies tend to be reddish in color because they are made up of older stars that emit more red light. These galaxies have used up most of their gas and dust, resulting in a lack of ongoing star formation. This makes their overall color appear reddish compared to younger, bluer galaxies.
At the center of the Local Group is a collection of ancient stars known as the Milky Way Galaxy. This galaxy is home to a significant number of old stars, many of which are located in its central bulge. Additionally, the Milky Way is surrounded by several other galaxies, including the Andromeda Galaxy and various dwarf galaxies, which together make up the Local Group.
Galaxies are vast collections of stars. So I guess you could say that a big group of stars forms a galaxy. Our galaxy has many big clusters of stars within it, so not all star clusters are galaxies. If you have a cluster of several million or billion (or trillion) stars surrounded by a lot of empty space, that is probably a galaxy.
In astronomy, a cluster is a large group of celestial bodies such as stars or galaxies.
No stars are actually a galaxy. All stars are stars and all galaxies are galaxies. Stars are found in galaxies. Some galaxies look like tiny dots in our night sky, so might look like a star, but they are not stars; they are galaxies.
All stars and galaxies are in the universe.