Astronomy ch 14 review

The letters AGN stand for _____.
an active galaxy nucleus

The energy from an AGN is produced by
matter flowing into a supermassive black hole.

All ____ galaxies are spiral galaxies that have small luminous nuclei.
Seyfert

In the double-exhaust model, the radio lobes of a radio galaxy are inflated by
jets of excited gas flowing from the central galaxy

The hot spots in double-lobed radio source
are where hot excited gas interacts with the intergalactic medium.

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.
quasar

The radio lobes that are on each side of some radio galaxies and jets from them produce mainly
synchrotron radiation

The fact that many radio lobes emit more intensely from the side away from the galaxy suggests that
they are created by jets from the galaxy emitting where the material is halted

The central galaxy in a double-lobed radio source is usually
a giant elliptical galaxy

The fact that the radio lobes radiate synchrotron radiation indicates that
high speed electrons are spiraling through a magnetic field.

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?
Centaurus A is probably the result of a merger of an elliptical galaxy and a spiral galaxy

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
emit a very large amount of energy per second

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
fluctuate rapidly on time scales as short as a few hour

We suspect that quasars are the active centers of galaxies because
“fuzz” around the central luminous regions produces spectra like a collection of normal stars.

The discovery of the gravitational lens effect for quasars
shows that quasars are much further away than the distant galaxy that forms the gravitational lens.

_____ galaxies contain a supermassive black hole at their centers while active nuclei are present in _____of galaxies
Most; a few percent

Galaxies may contain a supermassive black hole at their center but _____ an active nucleus because of _______ into the black hole
show; mass inflow

Statistical evidence
allows scientists to deduce general characteristics about a class of objects with similar properties.

What was the first evidence that quasars were different from astronomical objects before they were observed in visual wavelengths?
Quasars emitted radio energy like active galaxies, but appeared to be point sources in radio wavelengths.

Evidence that supports quasars being the nuclei of very distant galaxies includes
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.

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.
a supermassive black hole; an accretion disk

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).
Type 2 Seyfert (narow spectral emission lines; weaker x ray emission)

____ 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.
The gravitational lens effect

____ show(s) that some quasars are further away than distant galaxies and that space time is curved by massive objects.
The gravitational lens effect

Seyfert galaxies
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.

Quasars are most common with red shifts
of about 2

In the unified model of active galactic nuclei, the broad line region in an active galactic nucleus is
composed of clouds of gas and stars moving at very high orbital velocities near a supermassive black hole

The unified model describes active galactic nuclei using
a super massive black hole surrounded by an accretion disk and dense disk of gas.

What is the major observational difference between a Seyfert galaxy and a normal spiral galaxy?
The central region of a Seyfert galaxy is much brighter

How are astronomers able to determine that quasars are so small?
They are variable over a short period of time.

How do astronomers know that the luminous regions of active nuclei of active galaxies are very small?
The luminosity of the nuclei varies over short times

Why do astronomers believe supermassive black holes are the source of an AGN’s energy?
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.

Which kind of active galaxy has been observed at the greatest distances from us?
Quasars

How does the study of quasars reveal information of the history of the universe
Typical quasars are very distant so we can view how galaxy evolution occurred in the past.

The Milky Way galaxy is not a radio galaxy; it emits no radio radiation. T/F
False

Double-lobed radio galaxies appear to be emitting jets of gas and radiation. T/F
True

The radio radiation emitted by a radio lobe is mainly synchrotron radiation. T/F
True

Seyfert galaxies are spiral galaxies with active cores. T/F
True

Active galaxy radio lobes and jets contain magnetic fields. T/F
True

The rapid fluctuations of quasars show that the energy emitting portions of these objects must be very small.T/F
True

Quasar red shifts are usually larger than the red shifts of the visible galaxies. T/F
True

Some quasars have fuzz around them that produce spectra similar to normal galaxies. T/F
True

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