How do astronomers know that the luminous regions of active nuclei of active galaxies are very small?
a. Their nuclei are much brighter than expected.
b. The orbits of stars near the center of the galactic nuclei are faster than expected.
c. The luminosity of the nuclei varies over short times.
d. The color of the nuclei is different than expected.
Question 2
Synchrotron radiation is produced
a. in planetary nebulae.
b. by red dwarfs.
c. in massive stars as their iron core collapses.
d. in supernova.
e. by neutrinos.
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