CL - Stars (remote)[40]-1 (1)
docx
keyboard_arrow_up
School
California State University, Bakersfield *
*We aren’t endorsed by this school
Course
1609
Subject
Astronomy
Date
Apr 30, 2024
Type
docx
Pages
15
Uploaded by crystalized47
Computer Lab – Stars
(Virtual Lab Remote Edition)
Star Data
Launch the Voyager 4 program from csub.apporto.com. Single-click on any bright star to
bring up its Info Panel. The Info Panel information has the following meanings:
Under the General tab:
Name:
The star's Arabic name and other common names.
The star's Bayer name is a Greek letter followed by the constellation. The Greek
letter Alpha usually indicates the brightest star in the constellation, Beta
would be the second brightest, and so on.
The Flamsteed Number of the star, for example "58 Ori" would mean this is the
58
th
star (counting west to east) in the Orion constellation.
The Harvard Revised (HR) number of the star in the Yale Catalog.
The Smithsonian Astrophysical Observatory (SAO) Catalog number.
The star's number in the Henry Draper (HD) Catalog of spectral types.
Plus, additional catalog numbers for the star.
Type:
Such as Star, Double Star, Moon, Variable Star, Constellation, Galaxy, etc.
Magnitude:
The apparent magnitude of the star, lower values mean brighter looking stars.
Right Ascension:
The star's right ascension. The year following the R.A. value is what year
this position was calculated for, the value changes year to year due to precession
and proper motion.
Declination:
The star's declination.
Distance:
The distance to the star in parsecs and light-years.
Size:
Stars will have no angular size listed because they appear as just a dot in the sky,
objects like planets and nebulae which have visible extent will have sizes.
Azimuth:
The azimuth of the star in the sky for the current viewing location and time.
Altitude:
The altitude of the star in the sky for the current viewing location and time.
Under the Visibility tab:
Name:
[Same as above.]
Rise:
Time and azimuth that the star rises.
Transit:
Time and altitude when the star crosses the meridian.
Set:
Time and azimuth that the star sets.
Midnight Transit:
Time of year when the star is visible all night.
Solar Conjunction:
Time of year when the star is near the Sun – it is not visible at all at night.
In Constellation:
The constellation in which the star resides.
Stars – 1
Under the Physical tab:
Name:
[Same as above.]
Spectral Type: The spectral class of the star (following the OBAFGKM system) followed by the
luminosity class of the star (a roman numeral between I and VII).
Color Index:
Exactly how this is calculated is not important. Hot, blue stars will have a color
index that is negative, white or yellow stars near zero, and cooler red stars will
have positive values.
Proper Motion:
The Proper Motion of the star, the rate at which it appears to move across
the celestial sphere, because of its actual motion through space (or the
combination of its movement and our Sun's movement). This gives the rate at
which both the Right Ascension and Declination of the star change with time in
arc seconds per year.
Radial Velocity:
The Radial Velocity of the star, how fast it is moving towards or away
from the Earth and Sun. Positive values are stars moving away.
Absolute Mag.:
The absolute magnitude of the star which is the apparent magnitude the
star would have if viewed from a distance of 10 parsecs. The absolute magnitude
is a way of stating the star's luminosity, how much total light it emits.
Temperature:
The star's surface temperature in Kelvin.
Questions: [Selected answers are given at the end of these instructions.]
1.
For the star you chose, what is its:
(a)
common name?
Sirius
(b) type?
Double Star
(c)
distance away in light years?
8.601 ly
(d)
transit time today?
5:40 PM
(e)
spectral type?
A1Vm
(f)
direction of motion, towards us or away? [Hint: See the Radial Velocity entry above.]
Away
Stars – 2
(g)
absolute magnitude?
1.45
Magnitudes
The Voyager 4 program doesn't list the star's luminosity in watts nor does it list the
brightness we see in W/m
2
. Voyager uses an older system, the magnitude system. The star's
brightness is indicated by the "Magnitude:" value under the General tab.
The magnitude system dates back to Hipparchus who called the brightest stars
magnitude 1, next brightest magnitude 2, down to the dimmest stars visible with the naked-eye,
magnitude 6. The magnitude system is still in use today but in a slightly modified form.
Using telescopes, we can see stars dimmer than were visible to Hipparchus, these have
magnitudes like 7, 8, 9, etc. Note that dimmer objects have higher magnitude values. Because
we can measure the apparent brightness very accurately, we now allow magnitudes in-between
whole numbers, there are stars with magnitudes like 4.76 and 0.79. Very bright objects will have
magnitudes with negative numbers, the magnitude of the Sun is -26.7.
Use the Voyager 4 program to look up the magnitude of each of the following objects.
You can use menu choices under the Center menu to find all of these objects. Also fill in the
distances for the Moon (in km) and planets (in AU).
Object
Magnitude
Distance
Object
Magnitude
Distance
Moon
-11.8
4000214 km
Sirius
-1.44
8.6 LY
Sun
-26.7
1 AU
Betelgeuse
0.56
428 LY
Venus
-3.9
1.68210 AU
Polaris
2.00
431 LY
Mars
1.1
2.00992 AU
Orio
n
Nebula
4.00
1761 LY
Pluto
14.5
34.97701
AU
Andromed
a
Galaxy
3.50
3.13 MLY
Questions:
2. Which is brighter today, Venus or Sirius?
Sirius is brighter
3. Would you expect the Moon's magnitude to vary from day to day? Why? A lot or a little?
Yes, the Moon's magnitude does vary from day to day, but the variation is relatively small.
4. Can Pluto be seen with the naked eye?
No
These values are all apparent magnitudes, how bright they look, not how bright they
really are (their luminosity). The Andromeda Galaxy has the highest luminosity of all the
objects in this list, it puts out enough light that it can be seen with the naked-eye on Earth
Stars – 3
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
despite being over two million light-years away. No surprise it's so luminous, the Andromeda
Galaxy is the combined light of a trillion stars!
Of the objects in the above list, Pluto has the lowest luminosity. That’s because (1) it
emits no light on its own, (2) it is very far from the Sun, and (3) its small size means it reflects
little of the feeble sunlight reaching its vicinity.
Inverse-Square Law
The magnitude system indicates how bright objects appear to us. A lower magnitude
means brighter. In particular, every 5 steps of magnitude represent a factor of 100 in brightness.
So a star with magnitude -1 appears 100 times brighter to us than a star of magnitude +4.
How bright the star appears to us is determined by how much total light it emits and
how far away from us it is. The effect of distance on how bright the object looks is described by
the inverse-square law. It says that if we move n
times further away from an object that object
should appear n
2
times dimmer. Let’s check this using the Sun.
Select the Window/Location Panel menu and click on the
Solar System tab. Drag the Distance slider to 1 AU, you can just
leave the Longitude and Latitude values as they are. Select the
Center/Planets/Sun menu and record the magnitude value of the
Sun under the General tab) in the top line of the table below.
Sun:
Distance
Magnitude
1 AU
-26.72
10 AU
-21.72
100 AU
-16.72
You should've got -26.72 for the Sun's magnitude, this is the brightness of the Sun as
seen from Earth since the Earth is usually about 1 AU from the Sun. change the Distance slider
in the Location Panel to 10 AU. Record the new magnitude and repeat for a distance of 100 AU.
10 AU is 10x further from the Sun than 1 AU, so by the inverse-square law the Sun
should appear 10
2
= 100 times dimmer. But 100 times dimmer on the magnitude scale means 5
steps higher, so the Sun’s magnitude at 10 AU should be -26.72 + 5 = -21.72 . Was it? It’s another
factor of 10 in distance from 10 AU to 100 AU, so that should be five more steps of magnitude to
-16.7.
Question:
5. What would the magnitude of the Sun be if viewed from a distance of 1,000,000 AU? [You
can’t set this on Voyager, so you need to work out the answer mathematically. That’s six factors
of 10 (10
6
) further than the 1 AU distance so six factors of 100 in decreased brightness which is
six steps of 5 higher on the magnitude scale: -26.72 + 5 + 5 + … + 5 = ?]
3.28 magnitude
Stars – 4
6. The star Altair is about 1,000,000 AU (=15.8 LY) from the Sun. Would you be able to see the
Sun with the naked eye from Altair?
It's unlikely that the Sun would be visible with the naked eye from Altair.
Again, the further away from an object you are, the dimmer it will appear; but the
variation follows a well-understood law, the inverse-square law. If you know how much total
light a star emits (its luminosity) and how much light actually reaches us here on Earth (the
magnitude), you can calculate how far away the star is. The mathematics is complex, but the
concept is simple. Well, there is one complicating factor; interstellar (between stars) dust can
absorb some starlight causing dimming (“extinction”) separate from the inverse-square law.
Planetary Magnitudes
Select the Earth tab in the Location Panel, this should put you back on Earth viewing
from Bakersfield. Select the Tools/Planet Report… menu and then select the "Apparent
Magnitudes" option from the pop-up menu (probably after moving or hiding other windows).
Click the check boxes so that all the planets are selected (you can't select the Earth because we
are viewing from Earth and it doesn't appear in the sky), then click "Update". The chart shows
the magnitudes of these planets month-by-month for a year, you can click on “Next Interval”
and “Last Interval” to change years (that may be necessary to see some of the features described
below).
The white curve for Venus is almost always the highest, this means Venus is almost
always the brightest planet in our sky. Why Venus? For a few reasons; Venus is close to the
Earth, Venus is close to the Sun, and Venus is surrounded by clouds which reflect most of the
sunlight hitting them
Questions:
7. Mars is always closer to us than Jupiter, why is Jupiter usually brighter in our sky?
Jupiter's larger size and its relatively consistent distance from Earth result in its generally
brighter appearance compared to Mars in our sky.
8. Mercury's brightness (the brown line) rises and drops more than any other planet. What is
happening when it drops so low?
When Mercury's brightness drops significantly, it is typically due to its position near inferior
conjunction
The main factors determining what magnitude a planet will appear to have are
• how close it is to the Sun
(inverse-square law)
• how close it is to the Earth
(inverse-square law)
Stars – 5
• the size of the planet
(bigger reflects more light)
• phase as seen from Earth
(how much of reflected light heads our way)
• albedo of planet
(‘albedo’ measures how reflective the body is)
Magnitudes from Jupiter
Close the Planet Report window. Click on the Solar
System tab in the Location Panel, select Jupiter from the pop-up
window, and drag the distance slider down to zero. We are now
viewing from Jupiter's location.
Select the Tools/Planet Report… menu again. These lines now represent the varying
brightness of planets as seen from Jupiter. Sadly, Voyager won't let us turn on the plot for Earth
(a bug in the program); from Jupiter, Earth's brightness plot would be similar to that of Venus.
9. Which planet generally appears brightest in Jupiter's sky? Click the "Next Interval" button a
few times to make sure of your answer.
Venus
Star Colors
Select the File/Open Settings… menu, find the "110 Settings" folder, and open the
Settings File called "Enhanced Colors". The program is now displaying the stars with larger dots
and with brighter colors. Click on a bright star that appears blue in color to get its Info Panel.
Check the "Spectral Type" under the Physical tab for your star, it should be either type O or B (if
not, try clicking on another blue star).
The spectral class follows the OBAFGKM system, for example B8 or K3. The luminosity
class (listed immediately following the spectral class) is a Roman numeral with the following
meanings:
I (Ia and Ib)
Supergiant stars
II, III, IV
Giant stars (mostly Red Giants and Yellow Giants)
V, VI
Main Sequence Stars
VII
White Dwarf
Example: If the star’s “Spectral Type” says “G2V”, that means the star has spectral class G2 and
luminosity class V.
In the following table, record the spectral class (like M1 or G5), luminosity class (I, II, … ,
or VII), distance (in light years), magnitude, absolute magnitude ("Absolute Mag."), and
temperature for 12 stars. Remember, 'magnitude' measures the star's brightness in our sky while
'absolute magnitude
' measures its luminosity
(and that lower values mean more light).
Stars 1 and 2 on the list must be O or B types. Types 3 and 4 must be type A (they will
appear white or blue-white on screen). Stars 5 and 6 type F (white), 7 and 8 type G (yellow), 9
and 10 type K (orange), and 11 and 12 type M (red).
Stars – 6
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
If you are having difficulties finding stars of the right type (color), here is a trick that you
can use. Select the Display/Stars… menu and click on “Filter Stars by Spectral Type” and select
only the star type you want to find. After you click OK the displayed stars will all be just that
selected type.
Number
Type
Spectral
Class
Luminosi
ty Class
Distance
(LY)
Magnitud
e
Absolute
Magnitud
e
Temp.
(°K)
1
O or B
B3
IV
627.7 ly
4.73
-1.69
16400 °K
2
O or B
B9
III
634.5 ly
3.25
-3.20
11600 °K
3
A
A0
Va
25.297 ly
0.02
0.57
10000 °K
4
A
A7
V
16.773 ly
0.93
2.37
7400 °K
5
F
F3
IV
50.14 ly
3.36
2.43
7000 °K
6
F
F2
V
169.70 ly
4.76
1.18
6600 °K
7
G
G8
IV
44.71 ly
3.72
3.04
5000 °K
8
G
G9
III
108.68 ly
3.57
0.96
4700 °K
9
K
K3
II
460.7 ly
2.71
-3.04
3200 °K
10
K
K3
III
174.23 ly
3.84
0.20
3800 °K
11
M
M2
II
448.0 ly
3.82
-1.87
3800 °K
12
M
M0
III
1128.6 ly
7.26
-0.44
2500 °K
Questions: (give the star's Number from above to answer most questions)
10. Which star is furthest away?
12
11. Which star is closest?
4
12. Which star appears brightest in the sky? [Hint: Magnitude measures Apparent Brightness]
3
13. Which star appears dimmest in the sky?
12
14. Which star is the most luminous? [Hint: Don’t decide this based on Luminosity Class]
1
15. Which star is the least luminous?
11
Stars – 7
16. Which star is hottest?
1
17. Which star is coolest?
12
18. Of the 12 stars, Supergiant 1
Giant 4
how many were
Main Sequence 4
White Dwarf 0
19. (a) Will the closest star always be the brightest?
No, a far-away star can appear brighter if it has high enough luminosity.
(b) Was it in your case?
yes
20. (a) Will the brightest star always be the most luminous?
No, the most luminous may be too far away to appear brightest.
(b) Was it in your case?
Yes
21. (a) Will the most luminous star always be the hottest? No, the hottest star may be small and hence not as luminous.
(b) Was it in your case?
Yes
22. (a) Will the hottest star always be type O or B? Yes, the OBAFGKM system does rank stars from hottest to coldest.
(b) Was it in your case?
Yes
23. (a) Will the most luminous star always be a giant or supergiant? Usually, giant and supergiant stars are so much larger than main sequence stars that they almost always have greater luminosities.
(b) Was it in your case?
Yes
Stars – 8
24. If two stars have the same magnitude – that is they appear equally bright in the sky – but
one is much closer to us, which star is actually brighter (which star has the higher luminosity or
lower absolute magnitude, emits more light)?
The star that is farther away is actually brighter.
25. If two stars have the same absolute magnitude (the same luminosity), but one is hot (blue)
and the other is cool (red), which has the larger size?
Red star
Star Clusters
If you were previously filtering stars by type, turn that off. Select the Center/Common
Asterisms/Pleiades menu. An asterism is a group of stars that form a recognized pattern, but
which is not one of the official 88 constellations (an asterism might be a subset of stars within a
constellation or might be stars that connect across two or more constellations). Zoom to 3°. The
Pleiades is a star cluster, click the “Show” button in the Info Panel and you’ll see the seven
brightest stars of the cluster highlighted. The Pleiades is also known as The Seven Sisters. We
will assume that every star currently displayed is part of the Pleiades cluster.
Close the Info Panel. You are going to count the number of stars of each spectral type in
the region shown on screen and fill in the following table. In principle, you can tell the spectral
class of each star just by its color displayed on screen. In practice that just isn't going to work.
Select the Display/Stars… menu. Click on the check box next to "Filter Stars by Spectral Type",
you can now control which types of stars are displayed. Turn off all but types O and B, click
OK, then count the stars on screen and enter the total in the table. I expect you will count
between ten and twenty O and B stars; if not, you likely don’t have the correct settings (Did you
zoom to 3°? Are you still operating off of the Enhanced Colors settings file?).
Next turn on only type A and count. And so on. If you are having trouble counting the
stars left on screen you can turn on the grid option by clicking on the Grid button (
) along
the right edge of the window. Count all the stars on the screen, not just those that you think are
part of the cluster. You will repeat this for a second star cluster shortly to fill in the rest of the
table.
Pleiades (3°)
Hyades (4°)
Spectral
Type
Number
Seen
Percentage
(%)
Number
Seen
Percentage
(%)
O, B
14
15.56%
1
1.41%
A
34
37.78%
11
15.49%
F
20
22.22%
19
26.76%
G
14
15.56%
16
22.54%
K
8
8.89%
24
33.80%
M
0
0%
0
0%
Stars – 9
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Total
90
100%
71
100%
Calculate the total number of stars of all types and enter that at the bottom of the table.
The percentages are calculated as follows: divide the number seen by the total and multiply by
100%. For example, if you had 5 G-type stars in a cluster with 68 stars total, that would be
= 7.4 %
As a double-check, if you’ve calculated all the percentages correctly, they should add up to
100%.
Select the Center/Common Asterisms/Hyades menu, Zoom to 4°, and close the Info
Panel. Again count the stars of each spectral type, you should probably start with class M stars
because those are probably the only ones you're currently displaying! Make sure to turn off the
"Filter Stars by Spectral Types" option when finished.
H-R Diagrams
The Pleiades is a young cluster, it has many blue stars. The Hyades is an older cluster,
most of the blue stars are gone (they have gone supernova or evolved into red giants or white
dwarfs). The fraction of blue stars seen in a cluster can be used to date how old the cluster is.
A more precise way of determining a cluster's age is to make an H-R Diagram using the
stars of the cluster. Select the Tools/Star Survey… menu. Select "Color-Magnitude Diagram"
(which is another name for an H-R Diagram) in the upper-left pop-up menu. This shows a
standard H-R diagram but with all the low luminosity stars missing. All those red dwarfs and
white dwarfs are missing because this diagram is plotting "Naked Eye Stars" and the dwarf
stars are too dim to be seen with the naked eye from Earth.
Select "Stars within 20 Parsecs" in the upper-center pop-up menu. These are our
neighbor stars, a typical group of stars. Now dwarf stars are much more common. There should
still be even more dwarf stars in this chart because there are lots of dwarf stars within 20 parsecs
(65 light years) of Earth that haven't been discovered yet.
In an H-R Diagram for a specific star cluster, there are usually stars missing from the
upper end of the main sequence, stars that have become red giants (or gone supernova). Where
the main sequence ends (called the turnoff point because the line of stars going up the main
sequence often seems to turn off towards the red giant area) can be used to estimate the cluster's
age.
Select "Sky Chart Region" from the upper-center menu. You should now see an H-R
diagram using mostly stars in the Hyades cluster.
Star Masses
Accurate masses can be determined whenever we can measure the orbit of one object
around another (earlier in the semester we used the orbits of Jupiter's moons to determine the
Stars – 10
mass of Jupiter). We can use stars in binary systems (two stars orbiting each other) to determine
the masses of the stars. The mathematical formula is Newton's version of Kepler's third law,
D
3
= ( M
1
+ M
2
)
P
2
or
( M
1
+ M
2
)
= D
3 / P
2
where M
1
and M
2
are the masses of the stars in solar masses, D
is the distance between the stars
in AU, and P is the period of the orbit in years. The formula only determines the total mass of
the two stars, further information about the orbits is needed to figure out how much of the total
mass belongs to each star.
Our nearest stellar neighbor is Alpha Centauri which is actually a double star. Open the
Settings File "Alpha Centauri" and read the provided Info. Hold down the zoom "+" button until
you see α
1
Cen (Rigil Kentaurus) and α
2
Cen (Tollman) separated by one or two inches. Start the
animation.
26. What causes α
2
Cen to speed up and slow down?
The gravity from α1 Cen, it is following an elliptical orbit and obeying Kepler's 2nd Law.
Again, careful observations of double star systems allow calculation of the masses of the
stars. Now open the file "Zeta Cancri" and read the provided Info. Zoom in using the + button
or by selecting 30" from the zoom pop-up menu. Start the animation.
Q. Why doesn't ζ
2
Cnc move?
A. It does move, all three stars orbit each other around a common central point. It
doesn't move on screen because we have it locked at the center but we can change that. Change
the menu at the bottom of the screen from Equatorial to Galactic. Click on the nearby button to
unlock Zeta2 Cancri and then animate.
27. Which of the three stars has the most mass?
That would be the one that moves the least, ζ1 Cnc.
Now open the Settings File "Double Double", again read the Info then zoom in until you
see all four stars distinctly. Animate. The two pairs are about a sixth of a light-year apart and
the pairs take hundreds of thousands of years to orbit each other.
The Nearest Stars
Ask any child why some stars appear brighter than others and they might answer
because some are closer to us than others. That is certainly true for the Sun, it appears far
brighter to us than any other star because it is much closer to us. But for most stars, the closer
means brighter rule does not work very well.
Stars – 11
Our nearest neighbor stars can be displayed on the Voyager 4 screen. Select the
Tools/Solar Neighborhood… menu, select the "Star Names" option. This is a three-dimensional
view of the stars, move the scroll bars to rotate the view. You can also click on stars to get
information on the star and its location.
Here is a list of our nearest stellar neighbors. Use the table to answer the questions that
follow. There are 31 stars listed in the table, to calculate a percentage, divide the number by 31
and multiply by 100.
Distance
Spectral
Luminosity
Abs.
Star Name
(ly) Type
Class
Mag.
Sun
-
G2
V
4.85
Proxima Centauri
4.24
M5.5
V
15.5
Alpha Centauri A
4.36
G2
V
4.38
Alpha Centauri B
4.36
K1
V
5.71
Barnard's Star
5.96
M4
V
13.2
Wolf 359
7.86
M6
V
16.6
Lalande 21185
8.31
M2
V
10.4
Sirius A
8.66
A1
V
1.42
Sirius B
8.66
A2
VII (wd)
11.3
Luyten 726-8 A
8.79
M5.5
V
15.4
Luyten 726-8 B
8.79
M6
V
15.8
Ross 154
9.70
M3.5
V
13.1
Ross 248
10.3
M5.5
V
14.8
Epsilon Eridani
10.4
K2
V
6.19
Lacaille 9352
10.7
M0.5
V
9.75
Ross 128
11.0
M4
V
13.5
EZ Aquarii A
11.1
M5
V
15.3
EZ Aquarii B
11.1
M?
V
15.6
EZ Aquarii C
11.1
M?
V
17.4
61 Cygni A
11.4
K5
V
7.49
61 Cygni B
11.4
K7
V
8.31
Procyon A
11.4
F5
V
2.66
Procyon B
11.4
A?
VII (wd)
13.0
Struve 2398 A
11.5
M3
V
11.2
Struve 2398 B
11.5
M3.5
V
12.0
Groombridge 34 A
11.6
M1.5
V
10.3
Groombridge 34 B
11.6
M3.5
V
13.3
DX Cancri
11.7
M6.5
V
17.0
Tau Ceti
11.8
G8.5
V
5.68
Epsilon Indi
11.9
K5
V
6.89
Gliese 1061
12.0
M5.5
V
15.3
Questions:
Stars – 12
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
28. What percentage of the stars are part of a multiple star system (a star is part of a multiple
star system if it has an A, B, or C following its name, treat Proxima Centauri as if its name was
Alpha Centauri C). 18/31 = 58%
29. What percentage of the stars are:
(a) Type O: 0%
(b) Type B: 0% (c) Type A: 9.68%
(d) Type F: 3.23%
(e) Type G: 9.68%
(f) Type K: 16.13%
(g) Type M:
61.29%
(h) Giant or Supergiant: 3.23%
(i) Main Sequence: 93.55%
(j) Dwarf (white dwarf): 6.45%
30. What percentage are more luminous than our Sun (have a lower Abs. Mag.)?
16.13%
The Brightest Stars:
Bayer
Common
Spectral
Luminosity
Distance
Lum.
Name
Name
Type
Class
(ly) (L
sun
)
α
Cma
Sirius
A1
V
8.6
25
α
Car
Canopus
A9
I or II
310
13,500
α
Cen
Alpha Centauri
G2
V
4.4
2
α
Boo
Arcturus
K2
III
37
170
α
Lyr
Vega
A0
V
25
50
α
Aur
Capella
G8
III
43
150
β
Ori
Rigel
B8
I
860
120,000
α
Cmi
Procyon
F5
V
11.4
8
α
Ori
Betelgeuse
M2
I
640
60,000
α
Eri
Archernar
B3
V
144
3000
β
Cen
Hadar
B1
III
390
42,000
α
Aql
Altair
A7
V
17
11
α
Cru
Acrux
B0.5
IV
320
25,000
α
Tau
Aldebaran
K5
III
65
520
Stars – 13
α
Sco
Antares
M1.5
I
600
75,000
α
Vir
Spica
B1
IV
260
20,500
β
Gem
Pollux
K0
III
34
43
α
PsA
Fomalhaut
A3
V
25
17
α
Cyg
Deneb
A2
I
2600
200,000
β
Cru
Mimosa
B0.5
IV
350
34,000
Questions:
The above list contains 20 stars, calculate the percentages by dividing the number fitting
the category by 20 and then multiplying by 100%.
31. What percentage are:
(a) Type O 0%
(b) Type B 30%
(c) Type A 25%
(d) Type F 5% (e) Type G 10%
(f) Type K 15%
(g) Type M 10%
32. What percentage are:
(a) Giant or Supergiant: 25%
[These have Luminosity Class I, II, III, or IV.]
(b) Main Sequence: 50%
(c) Dwarf: 25%
33. What percentage were also on the Nearest Stars list? 0% (None of the stars on the list have
distances less than 12 light-years.)
That is, what percentage of stars on this list have distances less than 12 light-years?
34. What percentage are more luminous than our Sun (have a Lum. greater than 1)? 100%
35. Are any of the main-sequence stars on the list type K or M? No
36. Looking at the list, are there any stars closer than 50 ly that are more than 100 times the
luminosity of the Sun? Yes, two, name them: Alpha Centauri A, Alpha Centauri B
Answers to Questions:
1.
Answers vary
2.
Whichever has the lower magnitude, probably Venus.
3.
Yes, because of phases, a lot. The changing distance between the Earth and Moon
contributes only a small variation.
Stars – 14
4.
Answer hidden
5.
Answer hidden
6.
Answer hidden
7.
Answer hidden
8.
The dips occur, surprisingly, when Mercury is closest to us! That's when we see just its dark
side.
9.
Answer hidden
10 & 11. Look at Distance.
12 & 13. Look at Magnitude (lowest or most negative is brightest).
14 & 15. Look at Absolute Magnitude (lower or more negative is more luminous).
16 & 17. Look at Temperature.
18. Check their Luminosity Class (I supergiant; II, III, IV giant; V, VI main sequence; VII white dwarf).
19. (a) No, a far-away star can appear brighter if it has high enough luminosity.
20. (a) No, the most luminous may be too far away to appear brightest.
21. (a) No, the hottest star may be small and hence not as luminous.
22. (a) Yes, the OBAFGKM system does rank stars from hottest to coldest.
23. (a) Usually, giant and supergiant stars are so much larger than main sequence stars that they
almost always have greater luminosities.
24. Answer hidden
25. Answer hidden
26. The gravity from α
1
Cen, it is following an elliptical orbit and obeying Kepler's 2
nd
Law.
27. That would be the one that moves the least, ζ
1
Cnc.
28. 18/31 = 58%
29. Answer hidden
30. Answer hidden
31. (a) 0% (b) 30% (c), (d), (e), (f), (g) Answer hidden
32. Answer hidden
33. Answer hidden
34. 100%
35. No
36. Answer hidden
Stars – 15
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help