What kind of stars are found here?

A star in this region of the Hertzsprung-Russell diagram has a temperature of roughly 12,000 Kelvin (12,000 K), a luminosity 70 times greater than that of the Sun (70 × L_Sun), and a radius two times larger than the Sun (R = 2 × R_Sun). This star lies along the Main Sequence, where most stars (including the Sun) are found. The fairly high temperature indicates quite yellow (moderate) colours. You may have observed the "Dog Star" Sirius through a telescope - this is the region in which it is located.

Try to read the values of L, T, and R for yourself from the diagram. Do you estimate values for the luminosity, temperature, and size of the star similar to those listed above?

We can use the Stephan-Boltzmann Law to relate the temperature (T), size (R), and luminosity (L) of a star to each other. Measuring L, R, and T in solar units, we say that:

Let us say that the temperature of the star is exactly 11,600 K. We know that the temperature of the Sun is 5,800 K, so we can convert the temperature of the star into solar units. This is just a way of asking How hot is the star relative to the Sun? (If the star is four times as hot as the Sun, for example, T = 4 × T_Sun. If the star is one-fourth as hot as the Sun, T = 0.25 × T_Sun.)

This star is twice as hot as the Sun. Now assume that the radius of the star is exactly 2.13 times that of the Sun. (We don't need to convert this radius to solar units, as we are already using them.) The final step is to calculate the luminosity L, from T and R.

We estimated a value of L = 70 L_Sun from the diagram - an excellent match.