Supergiant stars like Rigel and Betelgeuse are the brightest stars in the universe in visible and infrared light.
Because they are so bright they can be used to study the properties of galaxies at greater distances than are possible with other kinds of stars. Studies are carried out with telescopes such as the Keck on Mauna Kea and the VLT in Chile, using visible light for studies of blue supergiant stars and infrared for studies of red supergiants.
These studies have demonstrated, for example, how element abundances in spiral galaxies decrease with distance from the galaxy nucleus; they have also led to Hubble’s Law being remeasured with unprecedented accuracy.
They have also shown how the star formation histories of more distant galaxies can be studied by obtaining spectra of so-called “Super Star Clusters”
“Using these stars, I can determine distances to each of these galaxies with high precision, and this is one of the few ways of knowing the size of our universe,” — Rolf-Peter Kudritzki