A star’s surface temperature reveals a stars color.
Stars can be classified by their surface temperatures as determined from Wien's Displacement Law, but this poses practical difficulties for distant stars.
Spectral characteristics offer a way to classify stars which gives information about temperature in a different way - particular absorption lines can be observed only for a certain range of temperatures because only in that range are the involved atomic energy levels populated. The standard classes are:
O: 30,000 - 60,000 K Blue stars
B: 10,000 - 30,000 K Blue-white stars
A: 7,500 - 10,000 K White stars
F: 6,000 - 7,500 K Yellow-white stars
G: 5,000 - 6,000 K Yellow stars (like the Sun)
K: 3,500 - 5,000K Yellow-orange stars
M: < 3,500 K Red stars
The commonly used mnemonic for the sequence of these classifications is "Oh Be A Fine Girl, Kiss Me".
Stargazing is for everybody. It’s for people who like seeing themselves as part of a bigger picture … people with a sense of wonder … people who just like being outside at night. Maybe that’s you. If so, here are 10 simple tips that can help you connect with the night sky, and have fun shared by Earthsky.org .