Epsilon Aurigae andEpsilon Aurigae andTeaching SpectroscopyTeaching Spectroscopy

Sally SeebodeSally SeebodeTeacher San Mateo High SchoolTeacher San Mateo High School

Graphic from Stencil , R., Sky & telescope, July 2009

Epsilon Aurigae SystemEpsilon Aurigae System

A binary system consisting of an F0I super giant A binary system consisting of an F0I super giant star being orbited by some sort of thin, dark disk. star being orbited by some sort of thin, dark disk. The disk varies in opacity and has a central hole The disk varies in opacity and has a central hole believed to be occupied by a pair of B stars. 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 SpectroscopyTeaching Spectroscopy

ConceptsConceptsWhite light is composed of many White light is composed of many different wavelengths.different wavelengths.When light passes through a medium, When light passes through a medium, some light is removed.some light is removed.Knowing what light is removed, tells us Knowing what light is removed, tells us about the substance(s) the light passed about the substance(s) the light passed through.through.Connect rainbow type spectra to 2 D Connect rainbow type spectra to 2 D graphical representation. graphical representation. (also distinguish (also distinguish between absorption and emission lines)between absorption and emission lines)

Teaching SpectroscopyTeaching SpectroscopyWhite light is composed of many different White light is composed of many different

wavelengthswavelengthsDemonstration: make a rainbowDemonstration: make a rainbowEquipment: Overhead projector, 2 sheets of paper to Equipment: Overhead projector, 2 sheets of paper to make a slit, a diffraction grating (Edmund Scientific 2 make a slit, a diffraction grating (Edmund Scientific 2 12” x 6” sheets $8.95 or 15 gratings $7.95)12” x 6” sheets $8.95 or 15 gratings $7.95)With sheets of paper, make a thin slit on overhead. With sheets of paper, make a thin slit on overhead. Place diffraction grating over projector lens.Place diffraction grating over projector lens.Show students that white light splits into rainbow of Show students that white light splits into rainbow of colors. Discuss colors and order/energy if appropriate.colors. Discuss colors and order/energy if appropriate.Students record colors as they see them and label Students record colors as they see them and label them appropriately. them appropriately.

Teaching SpectroscopyTeaching Spectroscopy

When light passes through a medium, some light is When light passes through a medium, some light is removedremoved

Demonstration: spectroscopy with filtersDemonstration: spectroscopy with filters

Equipment: Overhead projector, 2 sheets of paper to Equipment: Overhead projector, 2 sheets of paper to make a slit, diffraction grating, Arbor Scientific Color make a slit, diffraction grating, Arbor Scientific Color Filter Set (6 pack) ($12)Filter Set (6 pack) ($12)

Place filters over half of slit on overhead so diffraction Place filters over half of slit on overhead so diffraction grating is splitting white light and filtered light. grating is splitting white light and filtered light.

Students record colors from filtered light as they see Students record colors from filtered light as they see them. They make statements next to each spectrum them. They make statements next to each spectrum stating filter used and stating filter used and color(s) missing (absorbed)color(s) missing (absorbed). .

Teaching SpectroscopyTeaching Spectroscopy

Knowing what light is removed, tells us about Knowing what light is removed, tells us about the substance the light passed through.the substance the light passed through.

Spectrum of SunDescribe what you see?What did the sunlight pass through to create these black lines (absorption lines)?Photo from the Canadian Space Agency

Teaching SpectroscopyTeaching Spectroscopy

Connect rainbow type spectra to 2 D graphical Connect rainbow type spectra to 2 D graphical representation. representation.

Epsilon AurigaeApril 19, 2009

H gamma4340 Å

H delta4101 ÅCalcium II H

3970 Å

Calcium II K3930 Å

Teaching SpectroscopyTeaching SpectroscopyConnect rainbow type spectra to 2 D graphical Connect rainbow type spectra to 2 D graphical

representation. representation.

Our team at the College of San Mateo (CSM) is Our team at the College of San Mateo (CSM) is creating an archive of gray scale “rainbow like” creating an archive of gray scale “rainbow like” images of spectra matched with 2-D graphs. images of spectra matched with 2-D graphs. Our hope is to represent all spectral types and Our hope is to represent all spectral types and luminosity classes as well as variables and luminosity classes as well as variables and other interesting stars.other interesting stars.

Catalog website: Catalog website: http://collegeofsanmateo.edu/astronomy/imagehttp://collegeofsanmateo.edu/astronomy/images/SpectraCatalog.pdfs/SpectraCatalog.pdf

If pre-eclipse spectrum looks like this:If pre-eclipse spectrum looks like this:

What will partial and total eclipse look like?

Will we see spectral differences?Will we see spectral differences?

We hope so. Spectra of eclipsing AS 325 We hope so. Spectra of eclipsing AS 325 showed enlightening spectra.showed enlightening spectra.

B star eclipsed by a variable star.

Variable atmosphere like unknown disk of Eps Aur

Sample Spectral Changes from AS 325Sample Spectral Changes from AS 325

Notice weakening B star emission lines and new Ca II absorption lines around 4000

Howell, Johnson and Adamson, PASP, January 2009

Spectrum from outside eclipseSpectrum from outside eclipse

Spectrum from eclipse ingressSpectrum from eclipse ingress

weakeningnew

One place to find weekly spectraOne place to find weekly spectra

CSM is taking spectra of epsilon aurigae CSM is taking spectra of epsilon aurigae weekly (when visible) and posting them weekly (when visible) and posting them on its website. You can track the eclipse on its website. You can track the eclipse and see if there are changes in the and see if there are changes in the spectra.spectra.

Website: Website: http://collegeofsanmateo.edu/astronomy/http://collegeofsanmateo.edu/astronomy/observatory.aspobservatory.asp

This lesson fits into your curriculumThis lesson fits into your curriculum

Chemistry: atomic structureChemistry: atomic structure

Physics: lightPhysics: light

Astronomy: components of stars, Astronomy: components of stars, classification of stars (OBAFGKM), classification of stars (OBAFGKM), evolution of stars, etc. evolution of stars, etc.

88thth grade physical science grade physical science