Credit/Permission: For text, © David Jeffery. For figures etc., as specified with the figure etc. / Only for reading and use by the instructors and students of the UNLV astronomy laboratory course.
Sub Tasks:
This task is done with the
telescope
for IPI, but
with NO telescope
for RMI.
In fact, using the telescope
is primarily for practice using
the telescope since
the observations for actual results are done best by
naked-eye astronomy.
So RMI students
should just ignore any directions to use the
telescope
in this task.
Sub Tasks:
You have to fill in the star names TWICE since there are two panels in the
Observing Working Table.
Only one filled-in
Observing Working Table
is needed per group and it should be appended to the
favorite report form---unless your
instructor
asks for each group member to make fill-in
an Observing Working Table.
Have you done this?
Y / N
If stars look like
donuts and NOT
a bright points of light,
the C8 is out
of focus.
Do this while you observe using
naked eye---the
telescope does NOT help in
comparing brightnesses of stars
when doing visual astronomy.
The human eye perception of
brightness correlates with
apparent V magnitude.
Decreasing brightness approximates INCREASING
apparent V magnitude.
Do this while you observe using both
the naked eye
and the telescope---the
telescope may NOT really help much
in this job, but it's good practice to use it.
Redness decreases going red, orange, yellow, white, blue.
The human eye perception of
redness correlates with (color index) B-V.
Decreasing redness approximates DECREASING
B-V.
The KNOWN
data can be obtained from Wikipedia
by clicking on the star name in the
Table: Bright Stars to be Observed above
(local link /
general link)
Sub Tasks:
Have you done this?
Y / N
Note: The Libretexts image is from Libretexts: Blackbody Radiation.
For T = 4500 K using Wien's law
(see the figure above:
local link /
general link: wien_law.html),
calculate the peak wavelength λ
and by-eye determine its color band
(see the figure above:
local link: visible_band.html /
general link: visible_band.html).
Show your calculation and give the units
of the final wavelength answer.
The probability of a radially-traveling photon
(a particle of light) escaping from
a stellar photosphere
to infinity is about:
What are, respectively, the brightest and dimmest star classes in the
Ptolemaic magnitude system?
Order the following magnitudes
from brightest to dimmest: 0.0, -1.7, 4.5, 6.1, -3.2, 10.0, 22.5, -0.5.
To which passbands does
flux at
wavelength λ
= 5000 angstroms (Å)
= 0.5 microns (μm)
contribute according to
the figure above
(local link /
general link: photometry_ubvri.html)?
Sub Tasks:
Have you done this?
Y / N
You vary the
temperature
slider until
the panel B-V value equals
the B-V for the
main-sequence-stars
in the table below.
You are NOT matching the
temperature in the table which
CANNOT be done actually for T ≥ 25000 K anyway since that is the upper limit of
the applet.
Enter the fitted color temperatures
in the table below.
Sub Tasks:
Then go File/print preview/scale 100% or whatever fills the page/print.
Only one HR diagram is needed per group
and it should be appended to the
favorite report form---unless your
instructor
asks for each group member to make an
HR diagram.
RMI qualification: If you
do NOT have a printer,
hand draw the
HR diagram below
(local link /
general link: star_hr_lum_3.html)
as best you can
faute de mieux.
If there are multiple values for star,
the star is actually a
multiple star system
and we only want the first value.
You will have to interpolate as best you can for the
spectral subtype:
Note these are stars
of high apparent brightness and NOT necessarily of high
luminosity
(i.e., small absolute V magnitude).
Except use small X's
instead of small circles.
Stars on both lists
will have both a circle
and an X.
EOF
End of Task
RMI qualification:
If you do NOT have access to a
printer you will have to
hand sketch the
sky map or use
Google Sky.
_______________________________________________________________________________________
Table: Observing Working Table
_______________________________________________________________________________________
Brightness
_______________________________________________________________________________________
No. Common V Magni- Observed Brightness Observed Relative Actual Relative
Name tude (VB = very bright Brightness Brightness
(filled B = bright (1 = brightest (filled in
in post- M = middling 2 = 2nd brightest post-observation
observat- F = faint etc.) ranking by
ion) VF = very faint decreasing
U = unobserved) V magnitude,
1, 2, 3, etc.)
_______________________________________________________________________________________
1 | | | | |
2 | | | | |
3 | | | | |
4 | | | | |
5 | | | | |
6 | | | | |
7 | | | | |
8 | | | | |
9 | | | | |
10 | | | | |
11 | | | | |
12 | | | | |
13 | | | | |
14 | | | | |
15 | | | | |
_______________________________________________________________________________________
Color Index B-V or Redness
_______________________________________________________________________________________
No. Common B-V Observed Color Observed Relative Actual Relative
Name (filled (R = red B-V (i.e., Redness) B-V
in post- O = orange (1 = reddest (filled in
observat- Y = yellow 2 = 2nd reddest post-observation
ion W = white etc.) ranking by
B = blue decreasing B-V,
U = unobserved) 1, 2, 3, etc.)
_______________________________________________________________________________________
1 | | | | |
2 | | | | |
3 | | | | |
4 | | | | |
5 | | | | |
6 | | | | |
7 | | | | |
8 | | | | |
9 | | | | |
10 | | | | |
11 | | | | |
12 | | | | |
13 | | | | |
14 | | | | |
15 | | | | |
_______________________________________________________________________________________
T = (10**4 K)/ [(B-V) + 1] = (104 K) / [(B-V) + 1] .
to evaluate temperatures
for the B-V values and enter them in the
appropriate column in the table below.
_______________________________________________________________________________
Table: Characteristic Temperatures for Main-Sequence Stars
_______________________________________________________________________________
Stellar Class B-V Model Effective Blackbody Fit Crude Approximate
Temperature Color Temperature Formula Temperature
(K) (K) (K)
_______________________________________________________________________________
O5 V -0.33 42000
B0 V -0.30 30000
A0 V -0.02 9790
F0 V 0.30 7300
G0 V 0.58 5940
K0 V 0.81 5150
M0 V 1.40 3840
_______________________________________________________________________________
Note: The B-V and
effective temperature data are taken from
Wikipedia: Color index.
_______________________________________________________________________________
In fact, only use the brightest star of a
multiple star system even if the
stars are somehow listed separately
in Wikipedia: List of Brightest Stars.
For example, a G0 star is at the left edge of the G range, a G5 star in the middle,
and a G9 star at the right edge.
You do NOT have to be too precise, just get the points approximately correctly.
