Classification

- Demonstrate an understanding of how stars can be classified according to their spectral type
- Demonstrate an understanding that a star's colour is related to its temperature


Type

Colour

Temperature

Spectral lines

O

Violet -white

30,000° K+

Helium with Hydrogen

B

Blue-white

12,000 -
30,000° K

Hydrogen with Helium

A

White

8,000 -
12,000° K

Hydrogen Rich

F

Yellow-White

6,000 -
8,000° K

Calcium

G

Yellow

5,000 -
6,000° K

Some Iron lines

K

Orange

3,000 -
5,000 ° K

Many Metallic lines

M

Red

<3,000 ° K

Metallic and Carbon lines

Each of these types is divided into further categories of 0 to 9. The Sun is classed as a G2 star.

There are further categories of W (Hotter than O) and R, N & S (cooler than M). These are very rare stars and you don't need to know about these for the exam.

 

Animation New Window

HR animation Star Sizes

Image New Window




Links New Window

Imagine the Universe Stars and Types

Astronomy Picture of the Day Stellar Spectral Types: OBAFGKM

Exam Tip

Remember the types of stars by this helpful mnemonic:
Oh Be A Fine Girl Kiss Me


Question

Give an exmaple of how a star's colour is related to its temperature