STELLAR LAB # 1The Hertzprung-Russell DiagramIntroduction:The Hertzsprung-Russell (H-R) Diagram has become one of the most important ways inastronomy to categorize stars. In the H-R Diagram, each star is represented by a dot.There are lots of stars out there, so there are lots of dots. The position of each dot on thediagram tells us two things about each star: its luminosity (or absolute magnitude)relative to the sun and its stellar classification or temperature.The vertical axis represents the star’s luminosity or absolute magnitude. Luminosityrepresents the total energy emitted by the star, and is not dependent upon distance.Luminosity units are often multiples of the Sun’s luminosity. The absolutemagnitude of astar is another way to measure its intrinsic brightness.The horizontal axis represents the star’s surface temperature (notthe star’s coretemperature – we cannot see into the core of a star, only its surface). Usually this is labeledusing spectral type of the star or by using the Kelvin temperature scale.The H-R Diagram has proven to be extremely useful in interpreting stellar data based onthese patterns.Its development represented a major step forward in in understanding thelife cycles of stars.The position of a star on this diagram depends on where it is in its life cycle, as well as itsluminosity and surface temperature.Stars that are still fusing hydrogen in their core lie
