In the article, “A Million Stars Tell A Single Story”, Brian Koberlein tells us how we can study the lifespans of millions of stars using the Hertzsprung- Russell(HR) Diagram. HR Diagrams show the relationships between spectral type, absolute magnitude, temperature in Kelvin(K), and luminosity in solar units. We make a diagonal plot and lay out the stars; if the star is bluer, it is brighter. Red stars have a lower temperature than blue stars, but they are still bright. Most stars will lay among the main sequence that runs from the upper left to the bottom right of the diagram.
This article doesn’t just define what an HR Diagram is, but it goes in depth about how the properties of the stars are classified on the diagram; which is what the conceptual objective states. I took notes from the class lectures about how size is related to temperature and luminosity. For example, if the star is hot, it has a large radius, if it is medium, then it has a medium radius, and if it’s cool, then it has a small radius. Stars that are brighter and larger than expected are called giants or supergiants. We completed pages 117 and 118 in our Lecture Tutorials which had a similar diagram in the book as the one above.
This conceptual objective was more informative, because we got to calculate using the graph how astronomers actually classify stars.