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