What kind of stars are found here?

A star in this region of the Hertzsprung-Russell diagram has a temperature of roughly 36,000 Kelvin (36,400 K), a luminosity 155,000 times greater than that of the Sun (155,000 × L), and a radius roughly ten times larger than the Sun (R = 10 × R). This star lies along the Main Sequence, where most stars (including the Sun) are found. The high temperature indicates very blue (hot) colours. Located at the high end of the Main Sequence, this star is one of the brightest in the galaxy.

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 36,400 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 twice as hot as the Sun, for example, T = 2 × T. If the star is half as hot as the Sun, T = 0.5 × T.)

This star is roughly six times hotter than the Sun. Now assume that the radius of the star is exactly 9.96 × R. (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 similar value of L = 155,000 L from the diagram – so we did a good job working with our eyes!