Copy of HR Diagrams (1)
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School
Evergreen Valley College *
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Course
MISC
Subject
Astronomy
Date
Dec 6, 2023
Type
docx
Pages
4
Uploaded by nguyenpeyton
HR Diagrams
Background Information
Before you begin, read through
this background information
related to the lab.
Then complete
the following:
1.
The table below summarizes the relationship between spectral type, temperature, and
color for stars.
Use the background readings and the
Star Color Slider
to complete the
empty portions of the table. (If you are running stuck, use
this teacher video
for help.)
Star
Surface Temp(
K)
Spectral Type
Color
Betelguese
3,530
M2
Red
Arcturus
4,300
K5
Orange
The Sun
5,830
G2
Yellow
Procyon A
6,530
F5
Yellow-White
Sirius A
9,145
A1
White
Rigel A
11,000
B9
Blue-white
Delta Orionis
33,200
O9
Blue
2.
Complete the following table related to stellar luminosities in solar units using the
equation L = R
2
T
∙
4
.
If you are having trouble using this equation, then watch the video
Stellar Luminosity Table
, where I walk through the calculations.
Radius (R
⊙
)
Temperature (T
⊙
)
Luminosity (L
⊙
)
1
1
1
1
2
16.8
3.02
1
9
1
1/2
0.057
NAAP – HR Diagram Explorer
1
/
4
3.
The mass luminosity relation
describes the mathematical relationship between
luminosity and mass for main sequence stars.
It describes how a star with a mass of
2
M
⊙
would have a luminosity of [
11.3
]
L
⊙
while a star with luminosity of 3,160
L
⊙
would have an approximate mass of [
10
]
M
.
⊙
(Are you lost on this question - no clue
how to do it? Check out
this brief video tutorial
.)
HR Diagram Explorer
Open the
HR Diagram Explorer
.
Begin by familiarizing yourself with the capabilities of the
Hertzsprung-Russell Diagram Explorer through experimentation. (Running stuck on this section?
Watch
this teacher video
for help.)
●
An actual
HR Diagram
is provided in the upper right panel with an active location
indicated by a red x.
This active location can be dragged around the diagram.
The
options panel
allows you to control the variables plotted on the x-axis: (temperature, B-
V, or spectral type) and those plotted on the y-axis (luminosity or absolute magnitude).
One can also show the main sequence, luminosity classes, isoradius lines, or the
instability strip.
The
Plotted Stars
panel allows you to add various groups of stars to the
diagram.
●
The
Cursor Properties
panel has sliders for the temperature and luminosity of the active
location on the HR Diagram.
These can control the values of the active location or move
in response to the active location being
dragged. The temperature and luminosity (in
solar units) are used to solve for the radius of a star at the active location.
●
The
Size Comparison
panel in the upper left illustrates the star corresponding to the
active location on the HR Diagram.
Note that the size of the sun remains constant.
Exercises
●
Drag the active location around on the HR Diagram.
Note the resulting changes in the
temperature and luminosity sliders.
Now manipulate the temperature and luminosity
sliders and note the corresponding change in the active location.
4.
Check (with an “X”) the appropriate region of the HR diagram corresponding to each
description below.
Description
Top
Right
Bottom
Lef
Hot stars are found at the:
X
Faint stars are found at the:
X
Luminous stars are found at the:
X
Cool stars are found at the:
X
●
Drag the active location around on the HR Diagram once again.
This time focus on the
Size Comparison panel.
5.
Check (with an “X”)
the appropriate region of the HR diagram corresponding to each
description below.
Description
Upper
Lef
Upper
Right
Lower
Right
Lower
Lef
Large Blue stars are found at the:
X
Small Red stars are found at the:
X
Small Blue stars would be found at the:
X
Really Large Red stars are found at the:
X
●
Check
show isoradius lines
.
Note that at each point on a green line, stars have the same
value of radius.
Use these isoradius lines to check your answers in the table above.
●
In addition to the isoradius lines, check
show luminosity classes
.
This green region
(dwarfs V) is known as the main sequence and contains all stars that are fusing hydrogen
into helium as their primary energy source.
Over 90% of all stars fall in this region on
the HR diagram.
Move the active cursor up and down the main sequence and explore
the different values of stellar radius.
6.
Describe the range of
sizes of stars along the main sequence.
What are stars like near
the top of the main sequence, the middle, and the bottom?
At the top of the main sequence, the stars are large in size, highest in temperature and
luminosity, and are blue.
At the middle of the main sequence, stars are mid-sized, lower in luminosity (in
comparison to the stars at the top of the main sequence) and are closer to a white
hue. The temperature is also more than half the temperatures of the top stars.
The stars at the bottom of the main sequence are the smallest in size compared to the
other locations in the main sequence, along with their luminosity and temperature
being the lowest. They are also red/orange in color.
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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
.