Epsilon Aurigae and Teaching Spectroscopy

1. Epsilon Aurigae andTeaching Spectroscopy Sally Seebode Teacher San Mateo High School Graphic from Stencil , R., Sky & telescope, July 2009

2. 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.

3. 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)

4. 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.

5. 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).

6. 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

7. Teaching Spectroscopy Connect rainbow type spectra to 2 D graphical representation. H gamma 4340 Å H delta 4101 Å Calcium II H 3970 Å Calcium II K 3930 Å Epsilon Aurigae April 19, 2009

8. 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/images/SpectraCatalog.pdf

9. If pre-eclipse spectrum looks like this: What will partial and total eclipse look like?

10. 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

11. Sample Spectral Changes from AS 325 • Spectrum from outside eclipse Notice weakening B star emission lines and new Ca II absorption lines around 4000 weakening new • Spectrum from eclipse ingress Howell, Johnson and Adamson, PASP, January 2009

12. 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

13. 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