Which Observation of Quasars Convinced Astronomers That Quasars Were Very

question 227

Multiple Choice

Which observation of quasars convinced astronomers that quasars were very distant objects?

• A) an extremely red spectrum, reddened by extreme interstellar absorption of the blue part of the spectrum, meaning that the source must be a very long way away
• B) an extreme redshift of visible Balmer and UV Lyman hydrogen emission lines, indicating high recessional velocities and hence, by the Hubble law, very large distances
• C) extreme faintness at visible wavelengths; the inverse square law for visible light showed that they must be very distant
• D) appearing as pointlike star images under the highest magnification, meaning that they must be very far away

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