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.
The spectroscope is explicated
in the figure below
(local link /
general link: spectroscope.html)
and the
diffraction grating
in the figure below that
(local link /
general link: diffraction_grating.html).
Read the over the two figures. Have you done so?
Y / N
In this task,
we study the continuous spectrum
of the incandescent light bulb.
The
continuous spectrum
is to good approximation a blackbody spectrum
which we studied theoretically in
Lab 8: Stars: Blackbody Spectra.
For an explication of blackbody spectra,
see Blackbody file:
blackbody_spectra.html.
Sub Tasks:
In this task,
we consider further the
continuous spectrum
of the
incandescent light bulb.
Recall,
continuous spectrum
is to good approximation a blackbody spectrum
which we studied theoretically in
Lab 8: Stars: Blackbody Spectra.
For an explication of blackbody spectra,
see Blackbody file:
blackbody_spectra.html.
Sub Tasks:
Answer:
End of Task
In this task, we study the
line spectra
produced by a dilute gases
in spectral tubes.
A line spectrum consists of
a discrete set of spectral lines
that are sort of the images of the
slit aperture
of the spectroscope.
We discuss line spectrum theoretically
below in section
Quantized States and
section Grotrian Diagrams and Atomic Transitions.
Sub Tasks:
You should be cautious with the
spectral tubes
and absolutely do NOT touch exposed glass: it can be HOT.
Also the voltage of
the spectral tubes is very high, and
so be very cautious about anything that might be an
electrical conducting surface.
Except for the sodium spectral tube,
the spectral tubes
should be cycled on and off in 30 second periods (30 s on and 30 s off).
This just helps extend their lifetimes.
The only molecule currently available is
carbon dioxide (CO_2).
The other gases are
noble gases
(which ordinarily do NOT form
molecules)
or hydrogen (H)
(which at ordinary room
temperature
would be molecular hydrogen (H_2),
but in the spectral tube
is sufficiently hot to be
atomic hydrogen (H_I) gas).
Answer: Y/N
The formation of stellar spectra
is explicated in the two figures below
(local link /
general link: spectrum_formation.html;
local link /
general link: spectrum_formation_stellar.html).
Read the over the two figures. Have you done so?
Y / N
As simplified synthetic
solar spectrum
(in image representation) with the
Fraunhofer lines is displayed in the
figure below
(local link /
general link: fraunhofer_lines.html).
The Fraunhofer lines are the most
prominent and first discovered solar
absorption lines.
Since they were discovered before they could be identified with
atoms
and
molecules, they were designated by letters.
The letters have stuck.
Sub Tasks:
Sub Tasks:
Have you read it?
Y / N
Sub Tasks:
The CLASSIFICATION WINDOW has three graphs of
Intensity versus Wavelength
with wavelength in
angstroms (Å).
Note 1 nm = 10 Å and the
visible band fiducial range = 4000--7000 Å.
A list of standard
main-sequence stars
will appear at the right of the CLASSIFICATION WINDOW.
The list is NOT complete: NOT all
spectral subtypes
are shown:
usually only
spectral subtype
0 and 5.
You will have to
interpolate as best you can
to classify the
spectral subtypes
NOT listed.
Maybe with some imagination, classification to
spectral subtypes
1--3 and 6--9 is possible.
The sprectra of highlighted standard star on the list and the one below it are
displayed, respectively, in the top and bottom graphs.
The spectra are
absorption line spectra.
The troughs are the absorptions in the intensity representation of a sprectrum.
Scroll through the available standard star spectra by clicking on the standard star name:
O star
to M star.
Things you can do with the
CLASSIFICATION WINDOW (CW) and SPECTRAL LINE TABLE (SLT):
It's spectrum will be shown on the middle graph.
Go File/Display/Show Difference.
The top graph will show the standard star spectrum and
the bottom graph shows the difference spectrum: i.e.,
top spectrum minus the middle spectrum.
Now scroll up and down the standard star list.
When the difference is as flat as possible as judged by eye,
you have the best fit of a standard star to HD 124320.
What if you have two equally good fits.
These must be for adjacent standard stars?
Then HD 124320 must lie between those two standard stars in
spectral type
In fact, HD 124320 gets about an equally good fit from the A1 star and the A5 star.
So one interpolates to find the
subtype.
It seems HD 124320 is a bit closer to A1 than A5, and so our estimate is A2.
We enter A2 for HD 124320 in
Table: Best Fit Spectral Types below.
In this task, you answer questions about the
catalog-identified star
you classified
in Table: Best Fit Spectral Types
in Task 8.
Recall that all these stars
are main-sequence stars.
Sub Tasks:
Concert A
(frequency 440 Hz)
is the general muscial tuning
standard for musical pitch.
Say you had a 1-meter vibrating string
emitting concert A
sound
as its
fundamental.
What is the phase velocity
of the vibrating string waves?
Note you have to give a numerical value and its
unit.
HINT: You will have to have read over
section Quantized States to this point---as you should
have---and you
will have to do a little
algebra on the
frequency
formula in the figure above
(local link
general link: standing_waves.html)
to get a formula with v_phase = something
in algebraic symbols.
Note also that units
are treated just like
algebraic symbols since they are
algebraic symbols.
Say a quantum harmonic oscillator
does a transition between the n=7 and the n=3
energy levels and emits
a photon (a particle of
light) that carries away the lost
energy.
In units of ħω, how much
energy does the
photon have?
HINT: You will have to use the
formula shown in the figure above
(loca link /
general link: qm_harmonic_oscillator.html).
Sub Tasks:
What do you estimate to be the strongest and weakest
atomic hydrogen lines
in emission in the
visible band (fiducial range 0.4--0.7 μm)
extending the fiducial range a bit?
HINT: Recall
Task 6,
subsection Strong Atomic Transitions,
and the neutral hydrogen
Grotrian diagram shown in the figure above
(local link /
grotrian_01_00_H_I.html).
_____________________ , _____________________
The de Broglie relation
for calculating
photon energy
from photon
wavelength is
What is the photon energy range
visible light (fiducial range 0.4--0.7 μm)
using the fiducial range.
The lower energy level
of the He I 5876 Å line
is the upper energy level
of the _____________________ line which is in the
________________ wavelength band.
HINT: You need to consult the
Grotrian diagram of
He I above
(local link /
grotrian_02_00_He_I.html).
Atomic lines that arise from the
ground state of their parent
atom are usually very strong because the
ground state is usually overwhelming the
most occupied of any energy level.
Now the
Ca II H & K lines
and the Ca II 7291 Å and
7323 Å lines
both arise from the ground state
of Ca II.
However, the Ca II H & K lines are
usually much stronger. EXPLAIN why with the short answer in sentence form.
HINT:
You should read over subsection
Strong Atomic Transitions
and
Grotrian diagram of
Ca II
(local link /
general link: grotrian_20_01_Ca_II.html).
Above about what
atomic number Z would you expect
the elements
to have relatively weak
spectral lines in
astrophysical spectra? Why?
HINT: You should consult subsection
The Cosmic Composition
and the
solar composition figure above
(local link /
general link: solar_composition.html)
and note where there is a general decline to a definite lower abundance behavior
(excluding just the small Z region 1--6: i.e.,
hydrogen (H) to
carbon (C)).
Note that the expectation of weaker
spectral lines for high enough Z
is just a general one.
Intrinsic properties of some atoms for
the high Z region
may make some of their spectral lines
very strong in some circumstances.
EOF
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400 500 600 700
There should be set out some subset of the following
spectral tubes:
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400 500 600 700
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400 500 600 700
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_________________________________________________
Table: An Incomplete List of Fraunhofer Lines
_________________________________________________
Fraunhofer line Species Wavelengths
designation (nm)
_________________________________________________
A O_2 759.370
B
C
D_1
D_2
D_3 or d
F
G'
G_1
G_2
h
H
K
_________________________________________________
Star Spectral Type Photospheric
/Luminosity Temperature
Class (K)
Alcyone B7III 12753(147)
Aldebaran
Barnard's Star
Betelgeuse
Capella
Mizar A2V 9000(200)
Polaris
Procyon
Rigel
Sirius
Sun
61 Cygni
Note: Mizar is
a tricky case since it consists of
a double star with component
"stars"
Mizar A
and
Mizar B
and each component "star" is a
spectroscopic binary:
Mizar A
consisting of
Mizar Aa
and Mizar Ab;
Mizar B
consisting of
Mizar Ba
and Mizar Bb.
Mizar A
is much brighter than
Mizar B
and both its
binary companions are
A2V stars with
photospheric temperature
T = 9000(200) K.
_______________________________
Table: Best Fit Spectral Types
_______________________________
Star Spectral Type
_______________________________
HD 124320 A2
HD 37767
HD 35619
HD 23733
O 1015
HD 24189
HD 107399
HD 240334
HD 17647
BD +63 137
HD 66171
HZ 948
HD 35215
Feige 40
Feige 41
HD 6111
HD 23863
HD 221741
HD 242936
HD 5351
SAO 81292
HD 27685
HD 21619
HD 23511
HD 158659
_______________________________
E = hc/λ = (1.23984193 eV-μm)/(λ_μm) ,
where h is the Planck constant,
c is the vacuum light speed,
λ is wavelength,
and
λ_μm is wavelength in microns.