An astounding discovery made in the 1960s was the identification of QSOs (quasi-stellar objects); extremely luminous objects which sat at great distances from the Milky Way galaxy. The spectra of QSOs were an oddity for many years in that they appeared to contain unknown lines (and hence unknown chemical elements). This was a mystery until Maarten Schmidt realized that the spectra were understandable if the spectra were highly redshifted, that is, if they had large z. The large z ===> large distance ===> large intrinsic power for QSOs, luminosities thousands of times larger than normal galaxies! In this exercise, we determine the redshift and distance to the QSO 3C273.
Below are two spectra. The top spectrum is that observed from 3C273. The lower one is a comparison spectrum to be used to determine the wavelengths of the hydrogen lines marked in the spectrum of 3C273. We see H delta, H gamma, and H beta marked on both spectra. The comparison spectrum is one that would be produced by a laboratory object, that is, by an object that is not moving toward or away from us.
1. Find the laboratory wavelengths for the H delta, H gamma, and H beta lines and enter the results in the Table.
2. Find the wavelengths for the H delta, H gamma, and H beta lines in the spectrum of 3C273 and enter the results in the Table.
3. Find the redshift z, based on the H delta, H gamma, and H beta lines and enter the results in the Table.