Galaxy Classification

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School

University of Washington *

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Course

101

Subject

Astronomy

Date

Apr 3, 2024

Type

docx

Pages

3

Uploaded by CaptainGoldfishMaster1201 on coursehero.com

Questions 1. Which type of galaxy is likely to contain many M-stars but few O- stars? Elliptical galaxies are the type of galaxy that are likely to contain many M-stars but few O-stars. 2. Which type of galaxies appear to have many young stars? Irregular and spiral galaxies appear to have many young stars. 3. Which type of galaxies are more likely to show evidence of dust? Spiral galaxies are more likely to show evidence of dust. 4. Would you predict that a galaxy that is experiencing active star formation contains a little or a lot of gas and dust? Do your observations, as recorded in your table, support this assertion? Why or why not? If a galaxy is experiencing active star formation, it is likely to contain a lot of gas and dust. This is because gas and dust are the raw materials from which new stars form. Looking at my table of galaxy types, we can see that irregular and spiral galaxies are the most likely to be actively forming stars. These types of galaxies are also known to have a higher amount of gas and dust compared to elliptical galaxies, which are dominated by older stars and are not actively forming stars. So, the observations recorded in the table support the assertion that galaxies experiencing active star formation contain a lot of gas and dust. However, it is worth noting that there can be variations within each galaxy type, and some irregular or spiral galaxies may have less gas and dust than others . 5. Do galaxies that have many young stars also contain many old stars? Do your observations support this assertion? Why or why not? Galaxies that have many young stars do not necessarily contain many old stars. Irregular and spiral galaxies, which are more likely to have many young stars, can also have a significant number of older stars, particularly in their
central bulges. However, the overall mix of young and old stars can vary widely from galaxy to galaxy, and it is not necessarily true that a galaxy with many young stars will also have many old stars. 6. Consider the following conversation among three students: o Student 1: Because there is mainly red light in this galaxy and no blue light, I think that only small, red stars formed in this galaxy and not any big blue ones. o Student 2: I disagree; it’s just that blue stars don’t last very long. I think the blue stars that may have been there in the past have already evolved into red giants, so the galaxy looks red due to the light from all the red giants. o Student 3: I think you’re both wrong. I thought that both blue stars and red giants live short lives, so they should both be gone. I think that all the blue stars that formed early on have evolved into red stars that are there now. So the galaxy appears red because it’s full of a lot of old, red stars that used to be the blue stars. Write a paragraph that first corrects their misconceptions, and then explain why the galaxy they are looking at looks red. Base your arguments on stellar evolution as described in Astro 101. It is true that blue stars are generally more massive and shorter-lived than red stars, it is not accurate to say that all blue stars will evolve into red giants or that all blue stars are gone from the galaxy. The reason why the galaxy looks red is due to the population of stars in the galaxy. Over time, stars evolve and change in color and luminosity, depending on their mass. Blue stars, which are more massive and hotter, have shorter lifespans and evolve more quickly than lower-mass stars like red giants. However, this does not mean that blue stars are necessarily absent from the galaxy or that all of them have evolved into red giants. Instead, what we observe in the galaxy is a population of stars that are currently at different stages in their evolution. Blue stars that formed early on in the galaxy's history may have evolved into red giants by now, but some younger blue stars may still be present in the galaxy. Additionally, many of the lower-mass stars in the galaxy will also be red, simply because they have longer lifetimes and thus make up a larger proportion of the overall population.
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