In the article, “HERTZSPRUNG-RUSSELL DIAGRAM“, by Fraser Cain from universetoday.com, talked about how astronomers organized stars using the H-R diagram. The Hertzsprung-Russell diagram was developed by astronomers Ejnar Hertzsprung and Henry Norris Russell in 1910. The first H-R diagram showed the spectral types on the horizontal axis and the absolute magnitude on the vertical. But more recent models of the diagram have multiple characteristics per axis, shown in the image below.
This article relates to our conceptual objective, “I can explain how astronomers use the Hertzsprung-Russell diagram to study properties of star”, because this article gave an introduction on how astronomers used to organize stars. The H-R diagram consist of absolute magnitude and luminosity on the vertical axis, and spectral class and temperature on the horizontal axis. There’s a diagonal line of stars called the main sequence stars and almost all stars fall into this category. These stars range from being large and small, and either being hot or less hot. The small group to the bottom left are called white dwarfs. These stars are usually very small, and are quiet hot. But, since they’re small in size, their luminosity and absolute magnitude is very low. The group of stars above towards the right of the main sequence stars, are called giants. These stars are relatively large compared to most stars. They have a high luminosity because of their size but have a very low temperature compared to other stars. The last group of stars are above the giants and they are called Supergiants. These stars are extremely large compared to most stars and are really bright and radiate a lot of energy. We’ve learned this in class using our lecture-tutorial. The pages associated with the conceptual objective are 117-118, these pages helped us understand how to read and use a H-R diagram. We also discussed about Supergiants even though they weren’t brought up in the lecture-tutorial.
After reading this article, I’ve now learned how to read this diagram since I was never really able to figure it out before. As you can see, main sequence stars are the most common group of stars and even our own sun is part of it. This diagram will be used far into the future due to new discoveries and the formation of stars.