Harvard University

Astronomy Lab and Clay Telescope


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The Spectrum of the Blue (or cloudy) Sky

Spectral lines are universal signatures of elements; the NaD lines have exactly the same wavelengths from our lamp (in emission) as in the Sun (in absorption) if we measured in the center of the Sun where there is no radial velocity componet of rotation. Precise measures of the wavelengths of lines from stars uniquely identify the elements and velocities of stars, and emission vs. absorption lines yield the relative temperature and density of the source regions. We are not going to point the telescope at the Sun because the Sun is much too bright for our detectors. We will instead point away from the Sun to capture the scattered Sunlight!