Spectroscopy over a wide wavelength range holds the key to understanding many astonomical phenomena, since it provides the means to study the temperature, density, pressure, chemical composition (abundances), velocity field, and total amount of gas. Even without detailed knowledge of their behaviour, spectroscopy can be used to classify objects e.g., for stellar classification.

Imaging studies can be used to provide important morphological information and, in certain circumstances - particularly when filter observations are made around emission features - quantitative information. Spectroscopy, even when used for purely continuum studies, provides more detail than imaging (certainly in the case of point sources!), and provides intensity information at points in wavelength, frequency, or velocity space. Note that pure continuum sources are rarely met in practice so, in nearly every case, the presence of emission or absorption features provides us with the information needed for understanding the amount, temperature, pressure, abundance, surface gravity, and velocity fields of gas or motions of stars and galaxies.

Even when "simply" used for classification techniques e.g., spectral classification of stars, spectroscopy provides us with information unobtainable by any other means. In addition, even when spectroscopy is used in a supporting role, such as in determining the redshift of extragalactic galaxies or quasars, the implications can have far-reaching results. Of late, spectroscopic techniques have come to the fore in other work of profound importance in following the motions of stars and, by implication, inferring the presence of companion stars or planets, and perhaps whole solar systems beyond our own.

In this course we will learn the outlines of what is required for quantitative spectroscopy and shall study a number of applications of the techniques.

Recommended texts:

D. Emerson, "Interpreting Astronomical Spectra,"
Cambridge University Press ISBN 0 471 94176 X
E. Bohm-Vitense, "Introduction to Stella Astrophysics-
Volume 2: Stars and Their Spectra,"
Cambridge University Press ISBN 0 521 34870 6
J.B. Kaler, "The Stars and their spectra,"
Cambridge University Press, ISBN 0521 30494 6

More detailed works:

D.F. Gray, "The observation and analysis of stellar atmospheres,"
Cambridge University Press, ISBN 0 521 40868 7
C. & M. Jaschek, "The Classification of Stars,"
Cambridge University Press, ISBN 0 521 38996 8

More general works:

C.R. Kitchin, "Astrophysical Techniques,"
Adam Hilger, ISBN 0 85274 484 6
C.R. Kitchin, "Stars, nebulae and the interstellar medium,"
Adam Hilger, ISBN 0 85274 581 8

Supporting information :

- click on a link (Word format)

Plots showing stellar spectra and line strengths

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email to: espeyb"at"tcd.ie

Last update: 15th December 2006