GS107FinalTakeHome_15AUG23(1)
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School
Rogue Community College *
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Course
107
Subject
Astronomy
Date
Dec 6, 2023
Type
docx
Pages
2
Uploaded by SuperHumanOxideBison32
Name:
Derek Greene
GS 107
Take-Home Final Exam
Over Weeks’ 5-7 Material
1.
Consider the HR Diagram shown below.
All of your answers will
necessarily be approximate. Please answer on the following page or a
separate sheet of paper.
A. If a star has a luminosity 1000 times that of the Sun at a temperature of
3,500 K, what would its radius be? (3 points)
~5.99752531x10
10
B.
For the above star, what would its mass be? (3 points)
~1,000 x larger than the sun
C.
Consider a particular star at 7000 K.
What color would it be?
(Hint:
blackbody radiation is helpful here.) (2 points)
Yellow
D. For the above star in part C, report a luminosity and radius that would fit
the criteria.
(There are many correct values). (3 points)
LUM= 10
2
Radius = 10R
0
2.
What would be the luminosities of a star of 100 solar masses (relative to the
Sun) based on the mass-luminosity relation?
(10 points)
3.846x10
28
3.
Consider a binary star system with each star essentially the same mass.
If
there is a distance of 10 AU between the two stars with a period of 5 years,
what is the mass of EACH star? (10 points)
~4.97x10^30 kg
4.
Multiple-Choice and Short Answer (2 points each)
A. __
E
__A star that starts out at a mass of 8 solar masses will end up in what
final state?
a.
White dwarf mostly made of helium
b.
White dwarf mostly made of carbon and oxygen
c.
White dwarf mostly made of oxygen, neon and magnesium
d.
Supernova that leaves a neutron star
e.
Supernova explosion that leaves a black hole
B.
How did this lecture and lab time work for you?
Would there be a better
time that you can suggest?
I found the lecture portion of class went well but as the class was not intended to be
online this term, my lab experience was suboptimal.
C.
With the late start (after 4
th
of July) for summer term, the end of the term
runs into other things people need to do.
Would you have been interested in
a six-week term?
Of course, that means longer lecture and lab times per
week.
I like shortened and condensed classes during the summer term. It is more work to do,
but you get it done in a shorter amount of time.
D. Even though the in-person labs were a bit “draft”-y, do you suspect that you
preferred in-person labs compared to what you would do for online labs?
As I was not in-person, I cannot comment on experience. But I do think the in-person
labs would have been fun and was sad that I missed out on those.
E.
Which is your favorite lab activity up to this point?
I think so far my favorite lab activity was the planetary systems
classification/ supernova lab.
5.
Consider a star whose mass is thirty-five (35) times as that of the Sun.
Describe the life of this star from protostar to what sort of object it finally
ends up as. (10 points)
A star 25 times the size of the sun would start out forming as clouds of
molecules are condensed due to gravity. Starting with the burning of helium
and then hydrogen, the star will continue to burn until carbon fusion starts
and fusion of heavier elements. At the end of its life fusing even elements as
heavy as iron. Eventually the star will collapse on its iron core resulting in a
supernova. From there it will become a neutron star or if the mass is large
enough, a black hole.
6.
What is the mass of a black hole (in solar masses) that has a radius of 5
miles (yes, I’m making you do a conversion here)? (10 points)
2.68224
7.
Consider a value for the Hubble constant 70 (km/s)/Mpc (the usual units).
Using this value, what is the age of the universe? (10 points)
14 billion years old
8.
One of the spectral lines in hydrogen is called the hydrogen alpha line
which has a wavelength of 656.28 nm (the red line we saw in the
spectroscopy lab) when one is at rest relative to the source.
If we measure
the hydrogen alpha line of a star at 680.00 nm, how fast is the star moving?
Is it moving away from us or towards us? (10 points)
A star at 680.00nm would be moving very fast away from us.
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