Harvard Classification Scheme
Class
Color
Prominent spectral lines
Surface Temp. (K)
O
Blue
Ionized helium, hydrogen
> 25,000
B
Blue-white
Neutral helium, hydrogen
11,000 – 25,000
A
White
Hydrogen, ionized sodium, ionized calcium
7,500 – 11,000
F
White
Hydrogen, ionized sodium and calcium; neutral sodium and calcium
6,000 – 7,500
G
Yellow
Neutral sodium and calcium, ionized calcium, ionized iron, ionized magnesium
5,000 – 6,000
K
Orange
Neutral calcium, neutral iron, neutral magnesium
3,500 – 5,000
M
Red
Neutral iron, neutral magnesium, and neutral titanium oxide (not shown)
< 3,500
Use the Harvard Classification Scheme (shown in the table above) to answer the following quesiton: The Sun contains spectral lines from neutral sodium and calcium as well as ionized calcium, magnesium and iron. Of the choices below, which could be the surface temperature of the Sun?
4,200 K
5,800 K
8,900 K
14,300 K