Page 2 - analysis-and-interpretation-of-astronomical-sp

Analysis and Interpretation of Astronomical Spectra 2

Table of Contents

1 Introduction ............................................................................................................. 7

2 Photons – Messengers from the Universe........................................................... 8

2.1 Photons – Carriers of Information ..................................................................................................8
2.2 The Duality of Waves and Particles ................................................................................................8
2.3 The Quantisation of the Electromagnetic Radiation......................................................................8
2.4 Properties of the Photons ................................................................................................................9
2.5 Photons – Carriers of Energy ..........................................................................................................9

3 The Continuum ......................................................................................................10

3.1 Black Body Radiation and the Course of the Continuum Level ................................................. 10
3.2 Plank's Radiation- and Wien's Displacement Law ...................................................................... 10
3.3 The Pseudo Continuum................................................................................................................. 11

4 Spectroscopic Wavelength Domains ..................................................................13

4.1 The Usable Spectral Range for Amateurs ................................................................................... 13
4.2 The Selection of the Spectral Range ........................................................................................... 13
4.3 Terminology of the Spectroscopic Wavelength Domains .......................................................... 14

5 Typology of the Spectra........................................................................................15

5.1 Continuous Spectrum.................................................................................................................... 15
5.2 Absorption Spectrum .................................................................................................................... 15
5.3 Emission Spectrum........................................................................................................................ 15
5.4 Absorption Band Spectrum........................................................................................................... 16
5.5 Band Spectrum with Inversely Running Intensity Gradient ....................................................... 16
5.6 Mixed Emission- and Absorption Spectrum ................................................................................ 17
5.7 Composite Spectrum..................................................................................................................... 17
5.8 Reflectance Spectrum................................................................................................................... 18
5.9 Cometary Spectrum ...................................................................................................................... 18

6 Form and Intensity of the Spectral Lines............................................................19

6.1 The Form of the Spectral Line ...................................................................................................... 19
6.2 The Information Content of the Line Shape ................................................................................ 19
6.3 Blends............................................................................................................................................. 19
6.4 The Saturation of an Absorption Line in the Spectral Diagram ................................................. 19
6.5 The Oversaturated Emission Line in the Spectral Diagram ....................................................... 20

7 The Measurement of the Spectral Lines.............................................................21

7.1 Methods and Reference Values of the Intensity Measurement ................................................ 21
7.2 Metrological Differences between Absorption and Emission Lines ......................................... 21
7.3 The Peak Intensity P...................................................................................................................... 22
7.4
7.5 Full Width at Half Maximum Height .............................................................................. 22
7.6 , Equivalent Width ................................................................................................................... 23
7.7 Normalised Equivalent Width ................................................................................................ 24
7.8 FWZI Full Width at Zero Intensity ............................................................................................ 24
7.9 Influence of the Spectrograph Resolution on the FWHM- and EW Values .............................. 24
7.10 Practical Consequences for the FWHM and EW Measurements .............................................. 26
7.11 The Measurement of the Wavelength ......................................................................................... 26
Additional Measurement Options ................................................................................................ 26