Lecture 14…What spectroscopy tells us about the nature of the stars The Solar Spectrum A beautiful example of Kirchoff’s Laws

But first, an illustration of how m (apparent magnitude), M (absolute magnitude) , and the relation to distance can tell us something interesting in astronomy: Cepheid variables

The prototype….Delta Cephei Iota (3.52) delta Epsilon (4.19) Zeta (3.35) Lambda(5.04)

The Importance of Cepheids…the Period-Luminosity Relation

Starlight…application of spectroscopy to stars Continuous spectrum gives surface temperature (Wien’s Law) Spectral lines give chemical composition, temperature (also), speed of rotation (How?) and other properties Examples of stellar spectra…what can we say?

Spectral classes of stars: O,B,A,F,G,K,M What can you say about the temperatures of these stars?

With information provided by spectroscopy, we can search for correlations between stellar properties

What the data show: the Hertzsprung-Russell Diagram Highest quality data from the Hipparchus spacecraft

The Hertzsprung-Russell Diagram and the Types of Stars See Figure 16.20 Types of stars, important terms Main Sequence Giants Supergiants White dwarfs What does it all mean?

Hertzsprung-Russell Diagram