Multiple Choice
How are rotation curves of spiral galaxies determined beyond radii where starlight can be detected?
A) by extrapolation
B) through observations of the 21 cm line of atomic hydrogen
C) through observations of spectral lines of dark matter
D) by watching the galaxies rotate over a period of years
E) by measuring the broadening of absorption lines
Correct Answer:
Verified
Correct Answer:
Verified
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