“Let There Be Light”

1. “Let There Be Light”

2. A (Very) Basic Introduction to the Science ofSPECTROSCOPY at Cameron Park Rotary Community Observatory

3. As the RoeheRosetta Stone p As the Rosetta Stone proved to be the key to deciphering ancient Egyptian Hieroglyphics, soinformation hidden within Spectra of celestial objects contains the fundamental secrets of astronomy

4. For thousands of years, humans have marveled at the beauty of rainbows… But it wasn’t until the 17th century that we began to understand what they were

5. History • 1671 – Newton “Discovered” the spectrum by passing white light through a prism.

6. History • 1671 – Newton “Discovered” the spectrum by passing white light through a prism. • 1814 – Using a higher quality prism, Fraunhofer discovered hundreds of dark lines crossing the Sun’s spectrum

7. History • 1671 – Newton “Discovered” the spectrum by passing white light through a prism. • 1814 – Using a higher quality prism, Fraunhofer discovered hundreds of dark lines crossing the Sun’s spectrum • 1859 – Bunsen & Kirchoff discovered that elements produce discrete spectral lines corresponding to a specific wavelength

8. Frequency & Wavelength Wavelength One Oscillation

9. Frequency & Wavelength The eye perceives discrete wavelengths as colors

10. Kirchoff’s Law • A hot incandescent gas or solid emits a Continuous Spectrum • A thin gas between a light source having a continuous spectrum and the observer displays an Absorption Spectrum of dark lines superimposed on the continuous spectrum • An incandescent thin or low-density gas emits an Emission Spectrum – Bright lines against a dark background

11. Kirchoff’s Law Absorption Lines Continuous Spectrum Emission Lines

12. Kirchoff’s Law Doubly-ionized Oxygen (OIII) Line Emission Spectral Line Absorption Spectral Line

13. What is Black Body Radiation? • Kirchoff found that an object that was good at absorbing radiation was also good at emitting it. • He postulated a perfect object that would, with total efficiency, absorb ALL radiation that hit it, and with equal efficiency, emit the maximum possible amount of radiation at all wavelengths. • He called this hypothetical object a Black Body & the emission Black Body Radiation. • Why is this important to understanding Spectra?

14. What is Black Body Radiation? Because Black Body radiation provides a perfect spectral continuum… • A Black Body spectrum doesn’t depend on the chemical nature of whatever is producing it, only on the object’s temperature. • Any observed variations from that perfect spectrum could tell us much about the actual radiating body (such as a star).

15. Such As? • The brighter the object is, the more radiation it emits. • An object’s light curve is (very) roughly bell-shaped, with long & short wave-lengths having relatively low emission values, and … • Mid-range wavelengths rising to peak levels. And… (This is a key point) • The hotter the object is, the shorter the wavelength at which the peak emission occurs, so…

16. Comparing spectra from two stars, you should be able to determine which star is hotter. Let’s look at some examples…

17. Remember the mnemonic for stellar types by temperature?Oh, Be AFine Girl, Kiss MeType O stars are very hot, and Type M stars are very cool.

18. Comparing Two Stellar Extremes • Vega (Spectral Type A) • Betelgeuse (Spectral Type M)

19. Which Star is Hotter?

20. Which Star is Hotter? Alpha Lyrae (Vega) is a hot Type A main-sequence star… While Mu Cephei is a cool Type M supergiant

21. What is required to do Spectroscopy at the Observatory?The components are relatively few and, relatively, inexpensive…

22. A quality Telescope Our existing 4” Apochromatic refractor for bright objects …Just remove the diagonal and insert the spectroscope

23. A quality Telescope Our new 17” Planewave Corrected Dall-Kirkham astrograph for faint objects …Just insert a 2”/1.25” reducer and install the spectroscope

24. What do the Spectroscope Components Look Like? A diffraction grating to spread the light into its component colors

25. What do the Spectroscope Components Look Like? A CCD camera to record the resulting spectrum

26. What do the Spectroscope Components Look Like? A computer with image-processing software

27. What can we expect from our spectroscope & software? • Obtain & store stellar & non-stellar absorption & emission spectra • Obtain & store comet data • Detect & identify molecular signatures in the upper atmospheres of cool stars (i.e. Carbon Stars) • Record the rapid evolution of future supernova events

28. Emission Spectra From NGC 7009The Saturn Nebula

29. Spectral Data on Comet GarraddObtained using RSPec software

30. How About some Dynamic Calculations? Early in 2011 a supernova was discovered in the galaxy Messier 101. Although 27 million light years away, the blast was easily observed worldwide through backyard telescopes. Known as SN2011fe, the supernova was observed for months by hundreds of visitors to the observatory. With our new equipment we will be able to do more than simply observe the next supernova.

31. M101 Before & After

32. Real Science Will Be Done • Chemical analysis of the blast components Analysis of the supernova emission lines • Speed of the expanding supernova shell Calculating the doppler effect on the spectra. Simple math is required.

33. Specific Location of SN2011fe

34. SN2011fe Research Steps

35. SN2011fe Research Steps A nanometer is 1 Billionth of a Meter An Ångstrom is 1/10th of a Nanometer

36. Doppler Shift of SN2011fe By applying data from our recorded spectrum, the speed at which the supernova shell is expanding towards us may be calculated. Using information found on the Web, we determine that the spectral rest wavelength for Silicon II (Si II) is 6,355 Ångstroms

37. SN2011fe Research Steps A nanometer is 1 Billionth of a Meter An Ångstrom is 1/10th of a Nanometer Si II = 6355Å

38. Doppler Shift of SN2011fe The chart shows that the wavelength of Si II has shifted to a higher frequency (blue-shift). This observed blue-shift is due to the element’s velocity toward us. So, how fast is the approach? • The rest-wavelength of Silicon II is 6,355 Ångstroms • The observed wavelength of Silicon II is 6,150 (est.) Ångstroms • Velocity = Change in Wavelength x (Speed of Light) Rest Wavelength • Velocity = ((6355 – 6150) / 6355) x 300,000 Kps • Velocity = 10,000 Km/second = 22,000,000 Mph

39. Is Spectroscopy for Everyone?Probably Not • The primary goal of the Community Observatory is to provide a quality astronomical experience for our visiting public. For this reason… • Except for extremely rare celestial events, observations should be programmed for mid-week or after public hours to avoid interruption of public viewing opportunities

40. Is Spectroscopy for Everyone? • It does not take the place of observational astronomy & public viewing • Docent training & practice will be required both for effective equipment operation & assisting students with academic projects • Provision of non-invasive setup time and a productive data-gathering plan is necessary

41. Developing a Path Forward • Install and calibrate the equipment • Recruit and train a core spectroscopy group from within the Docent team • Present the capabilities of the new instruments to interested astronomy instructors within the Los Rios Community College District (i.e. Hale-FLC, McDaid-SCC, Reagan-EDC, et al.) & EDCOE • Work with these instructors to incorporate hands-on spectroscopy into their class curricula

42. Question Time