The Crab nebula is
a. a planetary nebula.
b. a Bok globule.
c. an open cluster.
d. an absorption nebula.
e. a supernova remnant.
Question 2If the redshifts of quasars arise from the expansion of the universe yet they have brighter magnitudes than galaxies with the same redshifts, the quasar must
a. be very small.
b. be within the Local Group.
c. be a single star with an extremely large mass.
d. be moving toward Earth with a large radial velocity.
e. emit a very large amount of energy per second.
Question 3_________ is a form of electromagnetic radiation produced by rapidly moving electrons spiraling through magnetic fields.
a. Lagrangian radiation
b. Accretion
c. Ultraviolet radiation
d. Synchrotron radiation
e. Infrared radiation
Question 4Centaurus A is a radio galaxy that has a visible galaxy at the center. This central elliptical galaxy of Centaurus A is encircled by a ring of gas and dust, different from most elliptical galaxies. The dust ring orbits about an axis that is perpendicular to the axis of rotation of the elliptical galaxy. What does this suggest about this central elliptical galaxy of Centaurus A?
a. The radio jets have caused the dust disk to be driven around the elliptical galaxy.
b. There are at least two black holes at the center of the elliptical galaxy.
c. Centaurus A is probably the result of a merger of an elliptical galaxy and a spiral galaxy.
d. Dust is produced as the jets interact with the intergalactic medium.
e. Elliptical galaxies often contain dust that forms a disk along their rotation axis.
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