Eagle Creek Observatory
"Teaching young minds about the heavens"

Star Colors

What does a star’s color tell us? It tells us what temperature it is. Why would we be interested in a star’s temperature?
A star’s temperature tells scientists how quickly it is burning its fuel. Stars can be grouped into ten different classes and are designated by the letters O, B, A, F, G, K, M, R, N, S. The surface temperature and color of the star is directly related to the spectral class letter.

If you look at the chart below you will see the colors go from very, very red at the cool end to very blue at the hot end. What happens when you heat a piece of metal in a fire? First it starts glowing red, then it turns more orange and gradually turns to “white hot.”

If you have a dimmer on any of your lights try this. Turn the dimmer all the way up. When you do this the light shines white. As you turn it down the light turns yellow then orange then red then goes out as the filament goes from very hot to cold. Stars are the same. As you go from the cooler ones to the hotter ones they go from very, very red to orange to white to blue.

Class Temperature Color Example
RA Dec
Type-S <2,200 Extremely Red R CMi
07 08.7 +10 01
Type-N <3,200 Very Red VX And
00 19.9 +44 43
Type-R <3,200 Yellow-Red LW Cygnus
21 55.2 +50 30
Type-M 3,200 Red-Orange Alpha Sco (Antares)
16 29.4 -26 26
Type-K 5,000 Orange Alpha Boo (Arcturus)
14 15.6 +19 11
Type-G 6,000 Yellow Sun, Beta Aql (Alshain)
19 55.5 +06 24
Type-F 7,000 Yellow-White Alpha UMa (Polaris)
02 31.8 +89 16
Type-A 10,000 White Alpha Lyra (Vega)
18 36.9 +38 47
Type-B 23,000 Blue-White Eta Lyra
19 13.8 +39 09
Type-O 25,000 Very Blue Mintaka
05 32.0 -00 18
Click on the name of the star for more information about the star.

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©2002 Kevin Muenzler, Eagle Creek Observatory.

Table information from various other sources