O

Blue-violet

50,000–30,000

Ionized atoms, especially helium

Naos (घ Puppis), Mintaka (δ Orionis)

B

Blue-white

30,000–11,000

Neutral helium, some hydrogen

Spica (α Virginis), Rigel (β Orionis)

A

White

11,000–7500

Strong hydrogen, some ionized metals

Sirius (α Canis Majoris), Vega (α Lyrae)

F

Yellow-white

7500–5900

Hydrogen and ionized metals, such as calcium and iron

Canopus (α Carinae), Procyon (α Canis Minoris)

G

Yellow

5900–5200

Both neutral and ionized metals, especially ionized calcium

Sun, Capella (α Aurigae)

K

Orange

5200–3900

Neutral metals

Arcturus (α Boötis), Aldebaran (α Tauri)

M

Red-orange

3900–2500

Strong titanium oxide and some neutral calcium

Antares (α Scorpii), Betelgeuse (α Orionis)