Catch the Colors of Stars (all night)

Stars shine with a color that is controlled by their surface (or photospheric) temperature, and this is captured in their spectral classification. In mid-May every year, the three bright stars of the Summer Triangle asterism are climbing the eastern sky after dusk. Deneb, Vega, and Altair are A-class stars that appear blue-white to the eye and have temperatures in the range of 7,500 to 10,000 Kelvin. Arcturus, which dominates the southern sky in evening, is an orange, K-class giant star with a temperature of only 4,300 K. Chara, the fainter of Canes Venatici’s two stars, is a yellowish, G-class star with a temperature of 5,900 K, similar to our sun’s. Reddish Antares, the heart of Scorpius, which twinkles above the southern horizon, is an old M-class star with a low surface temperature of 3,500 K. You can estimate the temperatures of other stars by comparing their color to these bright reference stars.