Astronomy homework-The Hertzsprung-Russell diagram

starSun
Polaris
Vega
Sirius b
Rigel
Regulus
Wolf 359
Lacaille
Betelgeuse
Alpha Crucis
Achemar
Ceti
Procyon A
Procyon B
Altair
Alpha Centauri A
Alpha Centauri B
Alpha Centauri C
Lalande
Luyten A
Luyten B
Ross 154
Ross 248
Eridani e
Aldebaran
Ross 128
Cygni A
Cygni B
Aquarii d
Indi e
Achernar
Altair
Spica
Persei d
Persei z
Scorpii t
Arcturus
Ophiuch A
Antares
Sirius A
Barnard’s Star
Van Maanen’s Star
Canopus
Crucis a
Fomalhaut
temp (1000 K) luminosity (Lsun)
5.8
1
5.9
6
10.7
55
10.7
0.0024
11.8
40000
18
1000
2.7
0.00003
4.5
0.02
3.2
17000
4
21
24
2000
0.5
0.14
6.5
7.3
6.6
0.004
9
0.01
5.7
1.6
4.2
0.33
2.8
0.0001
3.2
0.0055
2.7
0.00006
2.7
0.00002
2.8
0.00041
2.7
0.00011
4.5
0.3
4.2
100
2.8
0.00054
4.2
0.084
3.9
0.039
9.4
24
4.2
0.14
14
200
8
11
21
2800
17
1300
24
16000
25
2500
4.5
1100
5.1
0.6
3.4
5000
10.4
23
2.8
0.00045
7.5
0.00016
7.4
1500
21
4000
14
9.5
Name______
The Hertzsprung-Russell diagram
In this lab, you will explore the relationship between luminosity and temperature, using data from
observations of real stars. The excel file accompanying this lab can be used to plot the luminosity vs
temperature for the stars. You can also open the file in csv format to do the same.
Open the file “Lab4_data.xlsx” to view the data. The leftmost column lists the names of 45 stars in our
galaxy. The surface temperatures of the stars, in units of 1000 Kelvin are in the second column. The third
column gives the luminosities of the stars, in units of solar luminosity, in other words, using the
luminosity of the sun as a unit. The first entry is the sun, with a surface temperature of 5800 K.
Begin by make a graph of the luminosity vs. temperature
for the first ten stars. If you are not familiar with using
Excel, you can follow these directions.
I am using Excel2016. Your steps may vary with the
version of Excel.
Highlight the temperatures and luminosities for the first
ten stars, select the “Insert” tab and in the “Charts”
section, select a “Scatter plot.” Click on the top left icon,
without lines connecting the dots.
A chart should show up on your screen. We
need to change a few things to view the data
correctly.
Select the x-axis, right click it, choose “Format Axis” and make Values in reverse order.
Select the y-axis, right click it, choose “Format Axis” and make it a Logarithmic scale. For “Horizontal axis
crosses” enter 0.000001, to accommodate our data range better.
Select the title and rename the plot. I called mine “HR diagram.”
When the chart is selected, to the right of the chart is a big “+” sign. Click it and select “Axis titles” to
label your axes.
Your plot should now look something like this. What observations can you make about the plot?
Now, click on the graph and drag down the cell selection to add the data from all of the stars to the
graph. Add a screenshot of your plot here:
What can you say about the graph now? How does plotting more stars compare with plotting only a
few? What trends and characteristics of the data do you notice?
Now visit the webpage at http://astro.unl.edu/naap/hr/animations/hr.html to bring up the interactive
Hertzsprung-Russell diagram made by the Astronomy Department of the University of Nebraska-Lincoln.
The page opens to the default of the temperature and luminosity of our sun.
Keep the temperature at 5800 K. What happens to the size and color of the star to the left of the sun as
you vary the luminosity, keeping the temperature constant?
Explain why this happens.
What happens to the position of the star on the H-R diagram?
Now, keep the luminosity at 1.0 Lʘ. What happens to the size and color of the star to the left of the sun
as you vary the temperature, leaving the luminosity constant?
Explain why this happens.
The red “x” marks the position of the star on the H-R diagram to the right. What happens to the position
of the star as you vary the temperature, keeping the luminosity constant?
Now, vary both temperature and luminosity. Set the temperature to 21000 K. What does the luminosity
need to be for the star to be located on the red line (the main sequence) on the plot to the right?
What is temperature of a main sequence star with a luminosity which is fifty times that of the Sun?
Click on the options to show the luminosity classes. Use the sliders for temperature and luminosity to
answer the following:
What is the temperature range for red giants?
What is the luminosity range for red giants?
What is the temperature range for white dwarfs?
What is the luminosity range for white dwarfs?
Now use the selections under “Plotted stars” to investigate the effect of plotting the nearest stars as
compared to the brightest stars.
Which regions in the H-R diagram have stars, when you select to show the brightest stars? Why?
Which regions in the H-R diagram have stars, when you select to show the nearest stars? Why?
I wish to thank the Nebraska Astronomy Applet Project for the use of their interactive software.
-Dr. Kathryn Hadley