Re: stellar spectra

[Leigh Palmer <palmer@SFU.CA>]

> Today we were talking about the red shift in class.I was explaining that
> the hydrogen lines are shifted towards the red end of the spectrum if the
> star is moving away from us. What bothers me is that the spectrum of the
> sun is a continuous spectrum with dark absorption lines.  How does one
> observe the hydrogen lines to see if there is a red shift?

The lines in the solar spectrum are, among others hydrogen
absorption lines. These "Fraunhofer lines" reveal the presence
of the chemical species which occupy the cooler regions of the
photosphere and chromosphere of the Sun, the outer layers which
are realtively opaque to the continuous blackbody spectrum from
the hotter regions below. Measuring the redshifts of these
absorption lines is what is done to measure other stars' radial
velocities relative to our Sun.

Leigh