The Temperature of a Star And its Composition

The Energy of an Photon A photon carries energy in inverse relation to its wavelength. Thus Short wavelength photons carry more energy This is why short wavelength/high frequency light carries more energy

The hotter something is the more energy it gives off Thus the hottest stars glow brightest in the shortest wavelengths… Their“white light” is tinted blue Cooler stars have a yellow tint to their “white light” And the coolest have a red tint

(See Formula on the Board) Wien’s law According to Wien’s Law… The temperature of the surface of a Star can be found using the brightest wavelength of light (color) that it gives off. The Formula for this is: (See Formula on the Board)

(Indicating significant trace elements) Composition of Stars By studying the absorption/emission spectrum of stars we can find the composition of the star. All stars are mostly hydrogen and helium but they also have important trace elements Stars are divided into Spectral Classes based on their brightest spectral lines (Indicating significant trace elements) , and their temperature.

Spectral Classes O 28,000 K - 50,000 K. Blue-white Ionized Helium Class Temperature Color Strong Lines O 28,000 K - 50,000 K. Blue-white Ionized Helium B 10,000 K - 28,000 K. Blue-white Helium A 7,500 K - 10,000 K. White Hydrogen F 6,000 K - 7,500 K. Creamy Ionized Calcium G 5,000 K - 6,000 K. Yellow Calcium K 3,500 K - 5,000 K. Orange Titanium Oxide M 2,500 K - 3,500 K. Red Titanium Oxide