A) Active galactic nuclei are only found in elliptical galaxies, but dormant black holes are found in all galaxy types.
B) The black holes in active galactic nuclei have much larger masses than those of dormant black holes.
C) The black holes in active galactic nuclei have much smaller masses than those of dormant black holes.
D) The black holes in active galactic nuclei have much more matter flowing into them.
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A) a rich cluster
B) a poor cluster
C) the Virgo cluster
D) a globular cluster
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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 centre 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.
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A) when light passes near a massive object and is deflected by the object's gravitational field
B) when a galaxy has a central black hole with an accretion disk
C) when the mass of a galaxy is greater than expected from the luminosity of the galaxy
D) when the mass of a galaxy is less than expected from the luminosity of the galaxy
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A) Quasars emitted radio energy like radio galaxies, but looked like stars in visible light.
B) Quasars showed significant gravitational lens effects.
C) The spectra of quasars looked like those of M dwarfs.
D) The large redshifts originally indicated that they were orbiting the centre of the Milky Way.
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A) as a supermassive black hole at the centre of a normal spiral galaxy
B) as a supermassive black hole surrounded by an accretion disk and a dense disk of gas
C) as an accretion disk around a neutron star
D) as a gravitationally lensed high-redshift galaxy
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A) Supernovae are extremely luminous and can outshine their galaxies.
B) Supernovae all have about the same luminosity.
C) Because supernovae are very energetic, they are not well understood.
D) Supernovae are rare, so you might have to wait a long time.
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A) size
B) shape
C) mass
D) colour
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B
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A) It is composed of clouds of gas and stars moving at very high orbital velocities near a supermassive black hole.
B) It is composed of a super massive black hole surrounded by empty space.
C) It is the region responsible for producing the bright continuous radiation from within the event horizon.
D) It is the region responsible for the narrow absorption lines seen in Type 2 Seyfert galaxies.
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A) It will turn into an irregular galaxy when it has used up all of its gas and dust.
B) It may result from the collision and merger of spiral galaxies.
C) It evolves from a single spiral galaxy when the spiral has used up all of its gas and dust.
D) It would become a starburst galaxy if it were to move through the hot intergalactic medium of a cluster.
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A) 1 million
B) 10 million
C) 1 billion
D) 100 billion
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The radio energy emitted by our galaxy c...View Answer
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Quasars, or quasi-stellar objects, are a...View Answer
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A) the different rates of star formation in spiral and elliptical galaxies
B) the different amounts of gas found in spiral and elliptical galaxies
C) the large range of sizes of elliptical galaxies found in clusters
D) the different fractions of galaxy types in rich clusters and poor clusters
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Astronomers have made several observations that have led them to believe that supermassive black holes lie at the centers of many galaxies. One key observation is the high velocities of stars and gas near the centers of galaxies. These high velocities can only be explained by the presence of a massive object, such as a supermassive black hole, exerting a strong gravitational pull.
Another observation is the presence of intense radiation and energy emissions coming from the centers of galaxies, known as active galactic nuclei. These emissions are thought to be caused by the accretion of material onto supermassive black holes, which heats up and emits radiation as it falls into the black hole.
Additionally, astronomers have observed the effects of gravitational lensing, where the gravity of a supermassive black hole bends and distorts light from objects behind it, providing indirect evidence for the presence of these massive objects at the centers of galaxies.
Overall, these observations, along with others, have led astronomers to believe that supermassive black holes are indeed common at the centers of many galaxies.
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