unit 3 HW 1 (Complete)
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Dec 6, 2023
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PHYS 1403
C.R. James
UNIT 3 HOMEWORK 1
Description: The table below provides an incomplete list of the magnitude and distance (from Earth) for five stars (A - E).
STEP 1: Determine the missing value for the Apparent Magnitude of star C
STEP 2: Determine whether the missing distances are MORE than 10 parsecs or LESS than 10 parsecs. Do not determine the exact values for these distances.
STEP 3: Determine through reasoning (not computing) whether the missing value for
the Absolute Magnitude for star D is 1, slightly greater than 1, slightly smaller than 1,
much greater than 1, or much smaller than 1.
Star Name
Apparent Magnitude
Absolute Magnitude
Distance from Earth
(parsecs)
A
-1
3
>10
B
5
1
<10
C
0
0
10
D
1
>1
10,000
E
3
3
10
A. Ranking Instructions: Rank the brightness (from greatest to least) of each star (A – E) as it would appear in the night sky. Note that it is not necessary, but may be helpful, to complete the table before making your rankings.
Ranking Order: Greatest 1 A 2 C 3 D 4 E 5 D
Least
Or, the brightness of each star would appear the same from Earth (indicate with check mark).
Carefully explain your reasoning for ranking this way:
I marked the stars this way because the question asked for the stars APPEARING bright, which means I should look at the apparent magnitudes.
B. Ranking Instructions: Rank the apparent magnitude number (from greatest to least) of each star (A – E).
Ranking Order: Greatest 1 A 2 C 3 D 4 E 5 B Least
Or, the apparent magnitude number of each star is the same. (indicate with check mark).
Carefully explain your reasoning for ranking this way:
I chose this ranking for this because Star A’s apparent magnitude is -1, making it the greatest on the list. Star C’s magnitude is 0, making it the second greatest with Star D (1),
Star E (3), and Star B (5) following suit.
C. Ranking Instructions: Rank the actual brightness or luminosity (from greatest to least) of each star (A – E).
Ranking Order: Greatest 1 D 2 C 3 B 4 E 5 A Least
Or, the actual brightness of each star is the same. (indicate with check mark).
Carefully explain your reasoning for ranking this way:
This is my selectio
n for this question because the distance plays a role in how bright/luminious
a star actually is
. Looki
ng at the distance and absolute magnitude of the stars, we can assume that D would be the brightest, while A would be the dimmest.
D. Ranking Instructions: Rank the absolute magnitude number (from greatest to least) of each star (A – E).
Ranking Order: Greatest 1 D 2 C 3 B 4 E 5 A
Least
Or, the absolute magnitude number of each star would be the same. (indicate with check mark).
Carefully explain your reasoning for ranking this way:
I ra
nked the stars like this because the absolute magnitudes should be sorted by which one
is more negative. The most negative number on the list is Star D because it would have to
be somewhere past Star C (0).
2.
Complete lecture tutorial pp 33-35 (Magnitudes). Paste a photo of your work here:
1.
a.
Apparent Magnitude.
b.
Absolute Magnitude.
2.
a.
The Moon.
b.
Mars would look brighter.
c. If this new object APPEARS dimmer than Mars, then its magnitude would have to be “greater” than +2.0 (which is Mars’ apparent magnitude). So maybe something
like +4.0 or even +5.0.
3. I agree with Student 1’s argument of a -2.0 apparent magnitude looking brighter than a +1.0 magnitude. The negative numbers are actually the more brighter/”bigger” numbers, so they will appear more brighter than the positive numbers.
4. Since Star Y APPEARS brighter than Star Z, this means that its apparent magnitude must be greater than the latter’s. I can assume that Star Y’s apparent magnitude could be something like -2.0, while Star Z’s apparent is 1.0 or 2.0. However, due to the fact that Star Y is actually not the brightest, this means that the absolute magnitude is less than Star Z’s; it could be something like 2 or 3, while Star Z is 0 or -1.0.
5. A, because the further away the star is, the dimmer it gets.
6.
a.
Star D. It’s apparent magnitude is 4, which is higher than Star C’s apparent magnitude of 5.
b.
Star A. Despire Star D having a bigger positive
number (4), that means its actually LESS brighter than Star A’s magnitude, which is 1.
c.
Star A is exactly 10 parsecs away, because it’s apparent and absolute magnitude is the same value (1).
d.
The apparent magnitude and absolute magnitude of Star A would remain the same even if it was 40 parsecs away.
7.
This star would be located near the Earth. The apparent magnitude given (-26.7) would imply that the star would have be bright, so I’m assuming that this star is the Sun, if it was located near Earth..
3.
Complete lecture tutorial pp 141-142 (HR Diagram). Paste a photo of your work here:
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1.
a.
Spectral Type: B
b.
Temperature: 18,000K
c.
Absolute Magnitude: 0
d.
Luminosity: ~100
2. Stars D and E have the same temperature (they are in the same temperature range of 5,000 to 10,000.)
3. Even though both of these stars have the same temperature, they have different luminosities, so
we can assume they have different sizes. They do have the same spectral type, which is F.
4.
Stars C and F have the same luminosties, which is .001.
5.
They share the same magnitude.
6.
Even though they have the same luminosities, they have different temperatures. Star C is around 20,000K and is a White Dwarf. Star F is below 5,000K and is located in the Main Sequence stars.
7.
Stars that have the same spectral type has the same Temperature.
8.
Stars that have the same magnitude has the same Luminosity. 9.
a.
Star B (Main Seuqence)
b.
Star F (Main Sequence)
c.
Star C (White Dwarf)
d.
Star G (Red Giants)
9.
Complete lecture tutorial p 46 (Spectroscopic Parallax). Paste a photo of your work here:
10.
If you plot luminosity against temperature for the stars in the universe, what do you find? Most of the stars lay in a line in a band, where temperature is directly related to the luminosity of the stars.
11.
Draw an HR diagram of SPECTRAL TYPE versus LUMINOSITY. Indicate the main sequence, red giant region, white dwarf region. 12.
Draw an HR diagram of TEMPERATURE versus ABSOLUTE MAGNITUDE.
13.
To answer the following questions, use terms like “bottom” or “top” or “right” or “Lower
left,” etc. On your HR diagrams, where are stars of …
a.
Low temperature? b.
Bottom right.
c.
Low absolute magnitude? d.
Bottom right.
e.
Low luminosity? f.
Bottom left.
g.
Where would you find spectral type O MAIN SEQUENCE stars?
h.
Somewhere upperleft to lower right, in a diagonal line. i.
Where would you find a low temperature MAIN SEQUENCE star?
j.
Lower right
k.
Where would you find a high temperature MAIN SEQUENCE star? Does it have a large or small absolute magnitude?
l.
They would be located at the upper left of the chart. It would have a small magnitude.
m.
Where would you find an M-type GIANT star?
n.
Upper right.
14.
If an astronomer assumes that a G2 star is on the main sequence, but later finds out that it is, in fact, a giant star, how does this affect the distance estimate for the star? Will its apparent magnitude be different from the first assumption? Will its absolute magnitude be different? In what direction?
This would affect the distance by making it appear much further than initially. The
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apparent brightness would not change, but it’s luminosity would be much larger. The absolute magnitude would also be smaller.