Download When light passes through a medium, some light is removed

Epsilon Aurigae and
Teaching Spectroscopy
Sally Seebode
Teacher San Mateo High School
Graphic from Stencil , R., Sky & telescope, July 2009
Epsilon Aurigae System
A binary system consisting of an F0I super giant
star being orbited by some sort of thin, dark disk.
The disk varies in opacity and has a central hole
believed to be occupied by a pair of B stars.
Spectroscopic measurements can be used to
understand the nature and composition of the disk.
Teaching Spectroscopy
Concepts
White light is composed of many
different wavelengths.
When light passes through a medium,
some light is removed.
Knowing what light is removed, tells us
about the substance(s) the light passed
through.
Connect rainbow type spectra to 2 D
graphical representation. (also distinguish
between absorption and emission lines)
Teaching Spectroscopy
White light is composed of many different
wavelengths
Demonstration: make a rainbow
Equipment: Overhead projector, 2 sheets of paper to
make a slit, a diffraction grating (Edmund Scientific 2
12” x 6” sheets $8.95 or 15 gratings $7.95)
With sheets of paper, make a thin slit on overhead.
Place diffraction grating over projector lens.
Show students that white light splits into rainbow of
colors. Discuss colors and order/energy if appropriate.
Students record colors as they see them and label
them appropriately.
Teaching Spectroscopy
When light passes through a medium, some light is
removed
Demonstration: spectroscopy with filters
Equipment: Overhead projector, 2 sheets of paper to
make a slit, diffraction grating, Arbor Scientific Color
Filter Set (6 pack) ($12)
Place filters over half of slit on overhead so diffraction
grating is splitting white light and filtered light.
Students record colors from filtered light as they see
them. They make statements next to each spectrum
stating filter used and color(s) missing (absorbed).
Teaching Spectroscopy
Knowing what light is removed, tells us about
the substance the light passed through.
Spectrum of Sun
Describe what you see?
What did the sunlight pass through to create these
black lines (absorption lines)?
Photo from the Canadian Space Agency
Teaching Spectroscopy
Connect rainbow type spectra to 2 D graphical
representation.
Calcium II H
3970 Å
H delta
4101 Å
H gamma
4340 Å
Calcium II K
3930 Å
Epsilon Aurigae
April 19, 2009
Teaching Spectroscopy
Connect rainbow type spectra to 2 D graphical
representation.
Our team at the College of San Mateo (CSM) is
creating an archive of gray scale “rainbow like”
images of spectra matched with 2-D graphs.
Our hope is to represent all spectral types and
luminosity classes as well as variables and
other interesting stars.
Catalog website:
http://collegeofsanmateo.edu/astronomy/image
s/SpectraCatalog.pdf
If pre-eclipse spectrum looks like this:
What will partial and total eclipse look like?
Will we see spectral differences?
We hope so. Spectra of eclipsing AS 325
showed enlightening spectra.
B star eclipsed
by a variable
star.
Variable
atmosphere
like unknown
disk of Eps Aur
Sample Spectral Changes from AS 325
Spectrum from outside eclipse
new
weakening
Spectrum from eclipse ingress
Notice weakening
B star emission
lines and new Ca
II absorption lines
around 4000
One place to find weekly spectra
CSM is taking spectra of epsilon aurigae
weekly (when visible) and posting them
on its website. You can track the eclipse
and see if there are changes in the
spectra.
Website:
http://collegeofsanmateo.edu/astronomy/
observatory.asp
This lesson fits into your curriculum
Chemistry: atomic structure
Physics: light
Astronomy: components of stars,
classification of stars (OBAFGKM),
evolution of stars, etc.
8th grade physical science