Some general astrophysics questions: Answer all! At what optical depth does T =

Question

Some general astrophysics questions: Answer all!

At what optical depth does T = Teff? What is the probability for a photon emitted from this location (headed outward) to escape to infinity? What is the approximate pressure at this location?

What does doppler broadening mean? What do the widths of observed lines tell us about the gravitational acceleration at the stellar photosphere? How is the equivalent width of the line related to the abundance of absorbing ions for weak lines? How does the temperature determine which lines are present?

Explanation / Answer

Doppler broadening means broadening of spectral lines due to the Doppler effect caused by a distribution of velocities of atoms or molecules. The widths of observed lines tells us the For weak lines the doppler effect core dominates and the depth of the all profiles points grow in proportion to the abundance. The ratio of light in two different color filters gives the temperature of the objects.Cooler objects will have red color and the red stars has the coolst and blue color gives high temperature and hence blue stars are hottest.The widths of the observed lines tells the intensity ofthe stars photosphere.

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