What are the different types of stars?

 There are several types of stars based on their sizes, temperatures, and luminosities. One of the most common star classification systems is the Morgan-Keenan (MK) spectral classification, which categorizes stars based on their spectral characteristics. The following are the main types:

1. O-type Stars: O-type stars have a surface temperature over 30,000 Kelvin and a high luminosity. These stars are rare because of their extreme heat and reactivity.

2. B-type Stars: B-type stars have surface temperatures ranging from 10,000 to 30,000 Kelvin, are hot and blue, and have moderate to high luminosity. They are less massive than O-type stars, but they are still more massive than the sun.

3. A-type Stars: Stars of the A type are white or bluish-white in color with temperatures between 7,500 and 10,000 Kelvin. They are smaller and less massive than stars of the B type but are much more massive than the Sun.

4. F-type Stars: F-type stars have similar size and mass to the Sun and yellow-white appearances.

5. G-type Stars: G-type stars are relatively stable and common. Our Sun is a G2V star, which makes it a G-type star. G-type stars have yellow colors and surface temperatures ranging from 5,000 to 6,000 Kelvin.

6. K-type Stars: There are two types of stars known as K-type and G-type stars: orange and blue stars. It is the K-type star that is smaller and cooler than the G-type star. An orange dwarf star, which is smaller and cooler than typical G-type stars, is called an orange dwarf star.

7. M-type Stars: M-type stars are the smallest and coolest of all stars; they are also called "red dwarfs" because their surface temperatures are below 3,500 Kelvin.

The above classification represents the main sequence of stars based on their spectral characteristics, along with other classifications for the different types of stars, such as white dwarfs, neutron stars, and black holes.