The article, “Why Are Stars Different Colors”, posted to universetoday.com relates to our 12 objective, “I can explain how astronomers use the Hertzsprung -Russell diagram to study properties of star” accordingly. To summarize the article, it begins by recognizing the different types of stars and how they are characterized. The first characteristic the article identifies is the composition of a star, stating that different elements emit different wavelengths of electromagnetic radiation when heated, which also essentially depicts the small change in color to these stars. Then, the article states the temperature, which we know that hot stars have a large radius, medium have a medium radius, and cool have a small radius,  and the distance that has an effect on stars. It discusses the Doppler Effect and how stars can either be red-or- blue shifted, which we already learned about. But the main thing that stands out about this article and relates to our objective is the explanation of the modern classification and stellar evolution. It states that modern astronomy classifies stars based off of their spectral class, temperature, size, and brightness. The H-R Diagram allows us, as well as astronomers, to study stars in a faster and easier way by plotting the surface temperatures of stars against their luinosities. The H-R Diagram also provides information about stellar radii because a star’s luminosity depends on both its surface temperature and its surface area or radius. Conveniently and to get a better understanding of what the article was discussing, they provided the diagram itself, which is similar to the one we saw from our lecture tutorial: The Hertzspirg-Russel diagram, showing the relation between star's color, AM. luminosity, and temperature. Credit: astronomy.starrynight.com

The article states that on average, stars in the “0-range”, aka white dwarfs, are hotter, larger, and more massive than other classes, while stars in the lower end, K and M (red dwarfs) are cooler. In the Stellar Evolution paragraph of this article, it discusses the main sequence and giants/super-giants stars. Based off from our class, we know that most stars fall along the main sequence that runs from the upper left to the lower right on the diagram, the stars in the upper right are called supergiants (very large and bright), and just below that are the giants (smaller in radius and lower in luminosity). From the diagram, astronomers determine both is luminosity and surface temperature off of the stars main sequences mass. From the short pages from the lecture tutorial book we did in class, we also were able to identify that stars of the same spectral type have the same temperature and stars of the same absolute magnitude number have the same luminosity. This article helped me to have an even better understanding of the Hertzspring-Russell Diagram and how it relates to the properties of stars. The H-R Diagram is a sufficient, graphical tool that is an easier way to classify stars and makes it all the more interesting. I definitely thought this was one of the easier and quicker objectives to learn and can say i know how to use/study the H-R Diagram correctly.


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