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School
University of British Columbia *
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Course
311
Subject
Astronomy
Date
Jan 9, 2024
Type
Pages
3
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ASTR 311 — Tutorial 5
Black Holes and Standard Candles
1
Experiment!
Download the Clock App from the following URL:
http://www.phas.ubc.ca/
~
heyl/RClockApp.jar
and run it. On a Mac you may have to click on the file while pressing the “Control” key. Or run it in your browser at the
following URL:
http://www.phas.ubc.ca/
~
heyl/RClockApp_js.html
.
This applet lets you search for a black hole. Unfortunately, the black hole is black and you see it against a black sky background.
So how can you find it? The idea is to use clocks to probe the space for the black hole. Here, our clocks are just flashing blue
lights, that flash once every second.
How to use the applet:
•
Create a new clock by clicking on ”New Clock”. You can have many clocks running at the same time.
•
Click the mouse button down on any clock and drag (while holding the mouse button down) the clock to a new location.
The clock will change colour and flashing rate depending on its distance to the black hole.
•
When you think you’ve found the black hole, position the mouse cursor over where you think the black hole is, hold down
the ”Shift” key on the computer keyboard, and click the mouse button. The screen will change to show you your results.
•
You can try and see how fast and how few clocks you need to find the black hole.
1. What TWO changes will happen to the clocks as they get near the black hole?
2. How long did it take you to locate the black hole and with how many clocks?
3. How can astronomers find a black hole in space?
2
Practice!
In this part you are going to learn about how astronomers can use standard candles to estimate the distances of distant galaxies.
The following are data collected from certain types of variable stars.
Data Set A
Data Set B
Period
Luminosity
1 day
200 L
5 days
1778 L
10 days
3162 L
20 days
5623 L
50 days
32000 L
Period
Luminosity
0.1 days
100 L
0.2 days
100 L
0.35 days
100 L
0.7 days
100 L
1 day
100 L
1. Plot the points on the graph provided
log
10
(Period
/
Day)
log
10
(Luminosity
/
L
)
2. What relationship between period and luminosity can you deduce for both classes of variable star, represented by the
two data sets?
3. Are these types of variable stars cataclysmic or intrinsic? Explain.
4. In addition to the classification you have made in question 3, which special type of variable stars correspond to each data
set?
3
Think About It!
1. We observe the following stars D, E, F and G to have pulsation periods of 0.4, 0.8, 15 and 35 days respectively.
(a) If all of the stars lie at the same distance list then in order of increasing apparent brightness.
(b) If all four stars appear to have the same brightness in our sky list them in order of increasing distance from us.
2. Name three other methods astronomers use to measure distances and describe how each of them work.
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