AST1120-lab7
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Apr 3, 2024
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AST 1120: Stellar Astronomy
Name:
Lab 7 (40 points) Supernovas & Their Remnants
Learning Goals
Explain how the conservation of angular momentum applies to a pulsar.
Describe the connection between heavy elements in the universe and supernova
explosions.
Describe how relativity changes our perception of times and distances Click the hyperlinks given to access articles with information needed for this lab. Then write your answers in your own words. Part 1 – Rotation of Crab Pulsar
Figure 1 - Crab Nebula in multiple wavelengths. X-ray: NASA/CXC/SAO; Optical: NASA/STScI; Infrared: NASA/JPL/Caltech; Radio: NSF/NRAO/VLA; Ultraviolet: ESA/XMM-Newton
In 1054, Chinese astronomers recorded a new star in the constellation Taurus that was bright enough to be visible during the day. This event is now recognized as a Type II supernova explosion. Though the star gradually faded from view, modern-day telescopes can look at the supernova remnant known as M1 or the Crab nebula. X-ray and radio telescopes also reveal a rapidly spinning neutron star near the center of the remnant – the Crab pulsar.
1.
Recall the conservation of angular momentum from earlier in the semester. Our Sun currently rotates about once per month (25 days). If we took the entire mass of the Sun and shrank it down to the size of Colorado Springs (or any major city),
what would happen to its rotation rate? Figure 2 - The lines across the top and bottom of the image represent normal stars of constant brightness. The dots across the center represent the Crab pulsar. Image credit: ESO, https://www.eso.org/public/images/eso9948h/
2.
Explain how you can tell from Figure 2 that the Crab pulsar is rotating.
2
Figure 3 - Note: 1000 milliseconds = 1 second. Notice that the curve shows 6 large peaks, each one followed by a smaller peak. Image credit: ESO, https://www.eso.org/public/usa/images/eso9948i/
3.
Measure the total time between the leftmost large peak and the rightmost large peak on Figure 3 (units of milliseconds). 4.
Divide your total time by 5 to get the rotation rate of the Crab pulsar in milliseconds (milliseconds per one rotation). 5.
Divide your answer in milliseconds per rotation by 1000 to get the rotation rate of the Crab pulsar in seconds (seconds per one rotation). It should be less than 1 second!
6.
Determine how many times the Crab pulsar spins each second using your rotation rate (rotations per one second). 1 divided by your rotation rate.
3
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1
rotation
your rotationrate
(
seconds
)
=
¿
rotations
/
second
7.
The Crab pulsar rotates once ever 33 milliseconds or 30.2 times per second. Use
30.2 rotations per second as the known value and your answer above as data. Determine the percent error in your measurement of the rotation rate.
%
error
=
|
(
(
data
−
known
)
known
)
|
×
100
=
¿
8.
Think about this rotation rate compared to the rotation of our Sun of 1 rotation per
25 days. What can you say about the size of the Crab pulsar, compared to the size of our Sun? Explain your answer.
Part 2 – Supernova Remnants
For this portion of the lab, read this article about radioactive decay in supernova remnants
. 9.
Why was SN 1987A bright enough that it could be seen by eye?
10.What elements were detected in SN 1987A?
11.How much titanium was produced in SN 1987A?
12.What is a possible explanation for the large amount of titanium in SN 1987A?
4
James Webb Space Telescope made a recent discovery about SN 1987A
. Read the article and answer the following questions. 13.What type of supernova was SN 1987A?
14.What type of object was created at the center of the supernova during its explosion? 15.When were neutrinos detected from SN1987A? The next several questions refer to this article from the Chandra X-ray Observatory
. Figure 4 - Image Credit: Illustration: NASA/CXC/M. Weiss; X-ray: NASA/CXC/GSFC/U. Hwang & J. Laming
16.What evidence do we have that Cas A turned itself inside out during its supernova explosion?
5
17.How much of the remnant of Cas A is emitting X-rays?
18.How does the presence of titanium-44 in this supernova remnant tell us that this explosion happened relatively recently?
Part 3 – Time Dilation Use the time dilation calculator
linked here to fill in the table below and answer the following questions. Note, you want to use the 2
nd
box on that website, where it says “Enter a value for c and a distance then click Calculate:”
19.Enter percent of c and distance in light-years using the numbers given in Table 1.
Click Calculate and then fill in the rest of the table. I encourage you to round to 4 significant figures. For example, distance dilated to 1.905 light-years and spaceship time of 2.116 years. Table 1: Alpha Centauri, 4.37 light-years away
% of c
Distance dilated to (ly)
Time viewed from spaceship (years)
50
90
99.99
20.Explain why it is possible to get to Alpha Centauri in less than 4.37 years. Table 2: Center of Milky Way 26,000 ly away
% of c
Distance dilated to (ly)
Time viewed from spaceship (years)
6
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50
99
99.9999
99.999999
21.Under what circumstances is it possible to get to the Center of the Milky Way within a human lifetime? 22.If you traveled all the way to the Center of the Milky Way, would you want to return to Earth after your journey? Explain your answer. Figure 5 - Comparing a clock falling into a black hole with a clock outside of the black hole. Both clocks are viewed from an outside observer
You may want to look over Section 24.4 Time in Relativity
from the OpenStax Calculator.
23.Explain what happens to time on a clock that is falling into a black hole. 7
Conclusion
24.From the information in this lab, how do we know that pulsars are rotating? Give a specific example from this lab.
25.From the information in this lab, how do we know that supernova explosions form
heavy elements? Give a specific example from this lab.
8