Astronomy Chapter 24
A quasar consumes 1 solar mass of material per year, converting 15 percent of it directly into energy. What is the quasar's luminosity, in solar units?
2.2×10^12 solar luminosities
According to the Hubble Law, a galaxy with a velocity of 25,000 km/s will be
400 million pcs away.
Why do astronomers hypothesize that a massive black hole lies at the center of M 87?
A very small region at the center of M 87 releases an enormous amount of energy.
Imagine that when we looked out into the universe we found that the light from all galaxies was blueshifted (rather than redshifted) and that the light from the most distant galaxies was blueshifted by the greatest amount. Which statement best describes what we would conclude about the motions of galaxies in this case?
All are moving toward Earth, with distant galaxies moving faster than nearby galaxies.
Which of the following is true about the ages and masses of spiral and elliptical galaxies?
Both types are about the same age, but spirals vary less in mass.
A Cepheid variable star in the Virgo cluster has an absolute magnitude of -5 and is observed to have an apparent magnitude of 26.3. Use these figures to calculate the distance to the Virgo cluster.
D=1.8x10^7 pc
A spherical galaxy, like M87, which looks like a monster globular cluster, is type
E0
In Hubble's classification, which type of galaxy has no stellar disk and no gas or dust?
E0
The flattest of the ellipticals are class
E7
Assuming that the bright core of M 87 is powered by a supermassive black hole, which of the following best describes the source of energy that makes the core appear so bright?
Gravitational potential energy is converted to thermal energy as matter from the surrounding gas disk spirals into the central black hole.
Quasars usually have their distances measured by what technique?
Hubbles Law
In what sense are the quasars "quasi-stellar"?
In short time exposures, their images looked stellar.
The Large and Small Magellanic Clouds fall into Hubble's class:
Irr I.
Which statement about the Local Group is false?
It contains the large radio galaxy Centaurus A.
Which of the following paraphrases Hubble Law?
The greater the distance to a galaxy, the greater its redshift.
What is the nearest huge cluster of galaxies to our Local Group?
Virgo Cluster
What is the nearest huge cluster of thousands of galaxies, to which the Local Group may belong?
Virgo Cluster
Not only does the central engine of active galaxies and quasars require a black hole, but also ________ to provide the radiate energy.
an accretion disk of infalling matter
Synchrotron radiation produces a ________ spectrum.
continuous nonthermal
In this diagram, the galaxy at the left side is a(n)
elliptical
The greatest variation in size, mass, and luminosity occurs in
elliptical galaxies.
Quasar's spectral lines are:
emission lines with large red shifts.
According to Hubble's Law, the greater a galaxy's redshift, the
farther it is from us.
Most of the galaxies in the Local Group are
small ellipticals like the companions to M31 in Andromeda.
The type of radiation coming from active nuclei due to electrons spiraling in very strong magnetic fields at relativistic speeds is:
synchrotron radiation.
According to Hubble's law, with H0=70km/s/Mpc, how long will it take for the distance from the Milky Way Galaxy to the Virgo Cluster to double?
t = 3.1×10^17s
That quasars were at cosmological distances yet appeared like ordinary faint stars meant:
they must be producing such large quantities of energy than even fusion could not explain their output.
Suppose that galaxy B is twice as far from Earth as galaxy A. Hubble's law predicts that galaxy B will be moving away from Earth with approximately _____.
twice the velocity of galaxy A
In Hubble's classification, which type of galaxy has a small bulge and loose, widely spread, poorly defined spiral pattern?
SO
You observe a spiral galaxy with a large central bulge and tightly wrapped arms. It would be classified a
Sa
Which of the following is not one of Hubble's types of galaxies?
Seyfert spirals.