I will scan your star charts.

— Nomad, from Star Trek “The Changeling”

While reading “Entering Space” by Robert Zubrin, I chanced upon the subject of stellar classification. The Morgan-Keenan system goes from O-type, the hottest, to M-type, the coolest (Red dwarfs). Our own sun, Sol, is an example of a G-type star, which are on the cool side yet still hot and bright. Later, other types have been added, for example White Dwarfs are known as D-types. If humankind will someday journey to remote stars, it’s best to memorize this handy list!

The Morgan-Keenan system is as follows:

• O-type
• B-type
• A-type
• F-type
• G-type
• K-type
• M-type

This is sometimes remembered by the mnemonic “O be a fine gal/guy, kiss me.”

Further Reading:

https://en.wikipedia.org/wiki/Stellar_classification

https://en.wikipedia.org/wiki/Main_sequence

https://en.wikipedia.org/wiki/O-type_main-sequence_star

https://en.wikipedia.org/wiki/B-type_main-sequence_star

https://en.wikipedia.org/wiki/A-type_main-sequence_star

https://en.wikipedia.org/wiki/F-type_main-sequence_star

https://en.wikipedia.org/wiki/G-type_main-sequence_star

https://en.wikipedia.org/wiki/K-type_main-sequence_star

https://en.wikipedia.org/wiki/M-type_main-sequence_star

https://en.wikipedia.org/wiki/Annie_Jump_Cannon

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