Quasar Spectra Often Show Many Absorption Lines That All Appear

question 32

Multiple Choice

Quasar spectra often show many absorption lines that all appear to be due to the same electron transition (such as level 1 to level 2 in hydrogen) but that fall at different wavelengths in the spectrum.Why do we think this is the case?

• A)We are seeing absorption lines from clouds of gas that lie between us and the quasar,and therefore each cloud has a different redshift.
• B)Quasars are rotating rapidly,and this rotation produces spectral lines with a wide variety of Doppler shifts.
• C)The lines fall at different wavelengths because they are produced by different chemical elements.
• D)No one knows-it remains perhaps the greatest mystery about quasars.

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