Lab 5-Copy of Mapping Globular Clusters
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Arizona State University *
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Course
112
Subject
Astronomy
Date
Feb 20, 2024
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docx
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Mapping Globular Clusters
In this lab, our goal is to measure the distance from the Sun to the center of the Milky Way Galaxy. Finding the center of the galaxy is surprisingly difficult. It’s a bit like trying to find the center of a forest while you are wandering in and among the trees. Fortunately, the ancient star
clusters known as “globular clusters” provide an avenue for us to solve this problem. Globular clusters are evenly distributed around the center of a galaxy. They are also easy to identify in the night sky. Astronomers have discovered many globular clusters and carefully measured their distances. By graphing the location of these globular clusters, we can determine
the precise location of the center of our galaxy. Below is a table of globular clusters and their (x,
y) distance as measured from our solar system.
Cluster
x (kpc)
y (kpc)
NGC 104
3.79
-5.22
NGC 362
5.21
-8.47
NGC 1851
6.13
-12.85
NGC 2808
2.28
-10.53
NGC 3201
0.97
-7.79
NGC 4372
4.54
-7.71
NGC 4590
4.79
-8.44
NGC 5286
9.00
-10.15
NGC 5927
5.24
-3.46
NGC 6101
7.48
-6.18
Complete the instructions below and answer the reflection questions.
1.
Put a star at (0,0) on the graph below. This will represent the location of our sun. Remember that our sun is not
located at the center of the galaxy. (Has it been a while since you graphed data like this? Watch this brief teacher video
for review.) 2.
Using the data above, mark the location of each globular cluster on the graph below. (Here are a few options for how to do this: 1) You can print this document and graph by hand, 2) You can draw your own version of the graph with pencil and paper and graph the data, or 3) You can insert data points using the draw tool in Google Docs
. ) 3.
Since globular clusters are distributed evenly around the center of a galaxy, finding the approximate center of a group of globular clusters will allow us to determine the center of the galaxy itself. Estimate the center of the globular clusters on the graph below. Mark this location (which represents the galactic center) using a different color pen and record its x and y location in the table below.
x (kpc)
y (kpc)
Galactic
Center
4.7
-8
4.
Next we will calculate the straight-line distance from the Sun to the Galactic Center. You
can perform this calculation with the “
Pythagorean Theorem
” below, or you can simply use this “
Galactic Center Distance Calculator
” that I created for you. How many kiloparsecs is the Sun from the Galactic Center? 12.7 kpcs
5.
One kiloparsec (kpc) is 3,260 lightyears. So, we can calculate how many lightyears it is to
the galactic center by taking the distance in kpc (above) and multiplying by 3,260. Perform this calculation. How many lightyears is the sun from the center of our galaxy?
12.7 kpc X 3260 light years= 41, 402 light years from the sun to the center of our galaxy. The actual number of kpc is 8 from the sun to the center of the galaxy making it 26,080 light years away.
6.
If you were an astronomer, how would you improve this data set in order to make an even better measurement of the distance to the center of the galaxy? I think the data could be enhanced by refining our measurement methods for greater
accuracy. Due to the vast size of the universe, we currently rely on relative sizes for measurements. I hope for a method that allows us to collect precise and exact data.
Globular Cluster Graph
If drawn by hand, be sure to scan (or take a picture of) your completed graph and include it in this document. 0
1
2
3
4
5
6
7
8
9
10
-14
-12
-10
-8
-6
-4
-2
0
y (kpc)
Completing the Lab
1.
Return to the course and complete the lab quiz
to demonstrate your understanding. 2.
Submit your completed lab document using your instructor’s online dropbox
.
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