Spectral Class Estimator
Estimate which spectral class (O, B, A, F, G, K, M) a star belongs to based on its effective temperature.
Spectral Class Code
3
Spectral Class Code vs Effective Temperature
Formula
## Spectral Classification (OBAFGKM) Stars are classified by surface temperature into spectral types: | Class | Temperature Range | Colour | |-------|------------------|--------| | O | > 30 000 K | Blue | | B | 10 000 - 30 000 K | Blue-white | | A | 7 500 - 10 000 K | White | | F | 6 000 - 7 500 K | Yellow-white | | G | 5 200 - 6 000 K | Yellow | | K | 3 700 - 5 200 K | Orange | | M | < 3 700 K | Red | The output code: 7=O, 6=B, 5=A, 4=F, 3=G, 2=K, 1=M.
Exemplo Resolvido
The Sun at 5778 K.
- 015778 K falls between 5200 and 6000 K.
- 02Spectral class: G (code 3)
- 03Peak wavelength: 2897800 / 5778 = 501.5 nm (green)
- 04The Sun is a G2V star.
Perguntas Frequentes
What does OBAFGKM stand for?
The mnemonic "Oh Be A Fine Guy/Girl, Kiss Me" helps remember the order from hottest to coolest.
What are the subclasses (0-9)?
Each letter class is divided into 10 subclasses (0 = hotter, 9 = cooler). The Sun is G2, meaning near the hot end of the G class.
What about L, T, and Y classes?
These extend the sequence below M for brown dwarfs: L (1300-2000 K), T (500-1300 K), Y (< 500 K).