* Spectral Type: This is the most common way to categorize stars based on their surface temperature, which determines their color and the types of spectral lines they emit. The main spectral types, from hottest to coolest, are O, B, A, F, G, K, and M. Our sun is a G-type star.
* Luminosity Class: This describes a star's absolute magnitude, or intrinsic brightness. Roman numerals are used, with I being the brightest (supergiants) and V being the least bright (main-sequence stars).
* Size: Stars come in a wide range of sizes, from dwarfs to giants and supergiants.
* Mass: A star's mass is a key factor in its evolution and lifespan.
* Composition: While most stars are primarily hydrogen and helium, there are small variations in their chemical composition.
So, it's not accurate to say there are "five main groups." Instead, astronomers use a complex system of classifications to understand the diverse properties of stars.
