Astronomy ch 14 review – Flashcards
Unlock all answers in this set
Unlock answersquestion
The letters AGN stand for _____.
answer
an active galaxy nucleus
question
The energy from an AGN is produced by
answer
matter flowing into a supermassive black hole.
question
All ____ galaxies are spiral galaxies that have small luminous nuclei.
answer
Seyfert
question
In the double-exhaust model, the radio lobes of a radio galaxy are inflated by
answer
jets of excited gas flowing from the central galaxy
question
The hot spots in double-lobed radio source
answer
are where hot excited gas interacts with the intergalactic medium.
question
When discovered in the 1960's, a(n) ____ were found to emit large amounts of energy, but through visual and radio telescopes appeared to be a single point of light much like a star.
answer
quasar
question
The radio lobes that are on each side of some radio galaxies and jets from them produce mainly
answer
synchrotron radiation
question
The fact that many radio lobes emit more intensely from the side away from the galaxy suggests that
answer
they are created by jets from the galaxy emitting where the material is halted
question
The central galaxy in a double-lobed radio source is usually
answer
a giant elliptical galaxy
question
The fact that the radio lobes radiate synchrotron radiation indicates that
answer
high speed electrons are spiraling through a magnetic field.
question
Centaurus 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?
answer
Centaurus A is probably the result of a merger of an elliptical galaxy and a spiral galaxy
question
If the red shifts of quasars arise from the expansion of the universe yet they have brighter magnitudes than galaxies with the same red shifts, the quasar must be
answer
emit a very large amount of energy per second
question
Soon after discovery, it was observed that quasars had a star like appearance which was blurred by Earth's atmospheric "seeing". Despite the blurring, it was realized that the intense energy emitting regions of quasars must be small because they
answer
fluctuate rapidly on time scales as short as a few hour
question
We suspect that quasars are the active centers of galaxies because
answer
"fuzz" around the central luminous regions produces spectra like a collection of normal stars.
question
The discovery of the gravitational lens effect for quasars
answer
shows that quasars are much further away than the distant galaxy that forms the gravitational lens.
question
_____ galaxies contain a supermassive black hole at their centers while active nuclei are present in _____of galaxies
answer
Most; a few percent
question
Galaxies may contain a supermassive black hole at their center but _____ an active nucleus because of _______ into the black hole
answer
show; mass inflow
question
Statistical evidence
answer
allows scientists to deduce general characteristics about a class of objects with similar properties.
question
What was the first evidence that quasars were different from astronomical objects before they were observed in visual wavelengths?
answer
Quasars emitted radio energy like active galaxies, but appeared to be point sources in radio wavelengths.
question
Evidence that supports quasars being the nuclei of very distant galaxies includes
answer
1) the existence of quasar fuzz. 2) the observation of a supernova near a quasar whose distance from its brightness is consistent with the large redshift. 3) gravitational lensing of some quasars by nearby galaxies. 4) all of the above.
question
According to the unified model of active galactic nuclei, a(n) ____ is in the center surrounded by _________with a Type 1 Seyfert or Type 2 Seyfert being seen depending on the viewing angle.
answer
a supermassive black hole; an accretion disk
question
According to the unified model of active galactic nuclei, a ____ is observed if our line of sight is parallel to the plane of the dense disk of an active galactic nucleus (the direct view of the nucleus is blocked by dust in the disk).
answer
Type 2 Seyfert (narow spectral emission lines; weaker x ray emission)
question
____ is (are) observed when light from a distant quasar travels past a massive galaxy between us and the quasar, and this light is focused to form two or more images of the same quasar.
answer
The gravitational lens effect
question
____ show(s) that some quasars are further away than distant galaxies and that space time is curved by massive objects.
answer
The gravitational lens effect
question
Seyfert galaxies
answer
1) are more common in close pairs of galaxies than in isolated systems. 2) emit more energy at X-ray, ultraviolet, infrared, or radio wavelengths than normal spiral galaxies. 4) 1 and 2.
question
Quasars are most common with red shifts
answer
of about 2
question
In the unified model of active galactic nuclei, the broad line region in an active galactic nucleus is
answer
composed of clouds of gas and stars moving at very high orbital velocities near a supermassive black hole
question
The unified model describes active galactic nuclei using
answer
a super massive black hole surrounded by an accretion disk and dense disk of gas.
question
What is the major observational difference between a Seyfert galaxy and a normal spiral galaxy?
answer
The central region of a Seyfert galaxy is much brighter
question
How are astronomers able to determine that quasars are so small?
answer
They are variable over a short period of time.
question
How do astronomers know that the luminous regions of active nuclei of active galaxies are very small?
answer
The luminosity of the nuclei varies over short times
question
Why do astronomers believe supermassive black holes are the source of an AGN's energy?
answer
1) Such black holes have been found at the center of most galaxies both active and inactive. 2) Radio jets are seen from low mass black holes plus accretion disks inside our galaxy. 3) jets and accretion disks have been observed in active galaxies. 4) black holes can produce so much energy in such a small place. 5) all of the above.
question
Which kind of active galaxy has been observed at the greatest distances from us?
answer
Quasars
question
How does the study of quasars reveal information of the history of the universe
answer
Typical quasars are very distant so we can view how galaxy evolution occurred in the past.
question
The Milky Way galaxy is not a radio galaxy; it emits no radio radiation. T/F
answer
False
question
Double-lobed radio galaxies appear to be emitting jets of gas and radiation. T/F
answer
True
question
The radio radiation emitted by a radio lobe is mainly synchrotron radiation. T/F
answer
True
question
Seyfert galaxies are spiral galaxies with active cores. T/F
answer
True
question
Active galaxy radio lobes and jets contain magnetic fields. T/F
answer
True
question
The rapid fluctuations of quasars show that the energy emitting portions of these objects must be very small.T/F
answer
True
question
Quasar red shifts are usually larger than the red shifts of the visible galaxies. T/F
answer
True
question
Some quasars have fuzz around them that produce spectra similar to normal galaxies. T/F
answer
True
