The Atacama Large Millimeter/submillimeter Array (ALMA) will allow scientists to determine the radius and the rotation of stars and identify the chemical composition of dust being emitted from red supergiant stars (a star which is 10 to 1,000 times the diameter of our Sun, such as Betelgeuse).
One way in which a star is classified is by color (or spectra). Stars were first categorized in the 1890s by Annie Cannon. She used letters to classify the different spectra of light stars emitted. Originally the letters used were A through Q, since then, astronomers have narrowed and rearranged the classification index to the letters O, B, A F, G, K, M. O representing the hottest stars and M the coolest.
Below is a list of common stars and their attributes, the graph above represents how quickly the Atacama Large Millimeter Array will be able to detect these different stars.