PHYSICS 1306

EXAM III

Form 1                                                                                                                                                                                    Dr. Pinsky

Spring 2005

Your seat number is printed on your answer sheet

Sit ONLY in the seat corresponding to that number!

 

This is a CLOSED BOOK exam.  You may use a calculator, however you may not have any information stored in any user changeable memory prior to the beginning of the exam for any calculator that you use.  Warning: You may not have access to a cell phone or a pager at any time during the exam.  Keep your eyes on your own paper at all times.  THERE MAY BE MORE THAN ONE CORRECT ANSWER PER QUESTION, OR THERE MAY BE NO CORRECT ANSWERS FOR A QUESTION.  Mark all correct answers.  Grading will be RIGHT MINUS WRONG (answer by answer, not question by question).

DO  NOT  GUESS ! ! !

 

1           Concerning the visible interstellar matter within the Milky Way:

 

a       Dark nebulae are caused by dust.

b      Emission nebulae generally appear blue in color.

c       the mean density outside of nebulae is about one atom per cubic centimeter.

d      Reflection nebulae tend to occur very near hot young stars.

E      Emission nebulae generally show strong Helium lines in their spectra.

 

 2          Concerning the "bar" structure in a barred spiral galaxy:

 

a       the overall structure is thought by some astronomers to be the result of prior collisions between galaxies.

b      the orbital paths of the stars within the bar structure are actually highly elliptical.

c       their orbits are basically Keplerian (follow Kepler's Laws).

d      The spiral arms generally tend to come off of the center rather than the ends of the bar.

e       it is the most common shape for all galaxies as  generally classified by astronomers.

 

 3          Active Galactic Nuclei galaxies (AGNs) include galactic objects like:

 

a       All irregular galaxies.

b      the Magellenic Clouds.

c       Seyfert galaxies.

d      Pulsars.

e       those galaxies that have bi-polar jets creating giant radio-loud gas lobes on either side.

 

 4          In studying the Milky Way:

 

a       the spiral structure is best mapped using radio telescopes rather than in the optical wavelengths.

b      the nearest arms to the Sun can be seen directly only in the visible wavelengths.

c       the direction of the Sun’s motion cannot be reasonably determined.

d      important guidance can be obtained by studying other spiral galaxies.

e       we are in the best possible position to observe the details because we are in it.

 

 5          Which of the following observations bear directly on our present best estimate for the age of the universe?

 

a       the measurement of the apparent magnitude of type 1A supernovae in other galaxies.

b      the current temperature of the cosmic background radiation.

c       the age of the oldest life on Earth.

d      measurement of the Hubble constant as a function of distance.

e       estimates for the fraction of stars that form black holes at the end of their evolution.


 6          As seen from the Earth, the Milky Way:

 

a       appears as a band of stars and nebulae circling the earth in the sky that can be seen directly above the Earth’s equator.

b      appears to have its center at a point in the direction of the constellation Orion.

c       nuclear region can be seen distinctly in the radio wavelengths and shows evidence for the existence of a giant black hole.

d      is actually one of the smallest known spiral galaxies in our local supercluster.

e       in the direction of the galactic plane generally obscures our view of the rest of the universe beyond.

 

 7          M87, the giant galaxy in Virgo Cluster:

 

a       is a giant elliptical galaxy.

b      is at the center of our local supercluster.

c       was the first evidence cited by Hubble for the extra galactic nature of these nebulae.

d      is sometimes referred to as "Snickers".

e       shows evidence of the existence of a massive black hole in its galactic center.

 

 8          Quasars:

 

a       are all highly red shifted (not even one is blue shifted).

b      are generally all thought to be star-like or stellar objects in nature..

c       are thought to be due to jets pointed directly at us from giant black holes in their centers

d      all tend to be associated with our local supercluster.

e       are among the oldest compact sources in the universe that we can receive light from.

 

 9          Assume that the Hubble constant is 65 km/sec/Mpc.  Which of the following red shifts, z (where z = Dl/l ~ v/c), could be for objects NEARER than 100 Mpc (c = 3 x 105 km/sec):

 

a.  z = 1/3 x 10-2     

b.  z = 10-2    

c.  z = 1/3 x 10-1     

d.  z = 10-1

e.  z = 10-3     

 

10        The "dark matter" problem refers to:

 

a       the lack of sufficient "luminous" mass to account for observed gravitational effects of galaxies, and clusters of galaxies.

b      the tendency for stars in the galactic plane to have only smaller masses and lower brightness.

c       the disappearance of mass in the nuclear fusion process (hydrogen into helium).

d      the disappearance of mass from our universe by falling into black holes.

e       the unseen dust and gas that floats between stars in our galaky.

 

11        Evidence or arguments for possible giant black holes in the centers of galaxies comes in part from:

 

a       potential explanations for quasar energy sources.

b      the absence of light from these regions.

c       the appearance of relativistic jets from the nuclei of many different galaxies..

d      large Doppler shifts (blue and red) from stars in the central region of certain giant elliptical galaxies.

e       a full explanation of the missing mass problem.

 

 


12        Which of the following would likely be a very reasonable candidate for a star with a life bearing planet:

 

a       an M star in the galactic nucleus of a spiral galaxy.

b      an O star in the galactic disk of a spiral galaxy.   

c       an F star in the an elliptical galaxy.   

d      an F star in the galactic disk of a spiral galaxy.

e       a Population II G-2 star.

 

 

13        According to the Big Bang Theory:

 

a       the Universe is about 13.7 billion years old.

b      the 2.7 degree cosmic background radiation (CBR) is a remnant of all of the supernovae that have occurred since creation.

c       the farther away things are the faster they should appear to be moving away from us.

d      the universe is presently expanding.

e       at the earliest times the universe was filled with equal numbers of all "elementary" particles regardless of type.

 

 

14        The isotopy of the 2.7 degree cosmic background radiation:

 

a       proves the universe is very cold

b      was recently shown to be just sufficiently anisotropic enough to provide for the formation of galaxies.

c       implies that dark matter is non-baryonic.

d      refers to the uniformity of the intensity as a function of direction.

e       is an important constraint on our present best estimate for the age of the universe.

 

 

15        Assuming the Big Bang is correct, and the universe is accelerating:

 

a       the "knowable" universe will always be bigger than the "known" universe.

b      the "known" universe will always be limited by the then current age (time since the Big Bang).

c       the red shift must decrease with distance.

d      we will never stop expanding.

e       the expansion rate must have been slower in most recent past than it appears to be now

 

 

16        According to the Drake estimate of the probability that intelligent life exists elsewhere in the Milky Way at the present time, the issues one must consider include:

 

a       the number of Population I stars in the galaxy.

b      the likelihood that stars are not members of close multiple star systems.

c       the main sequence lifetime of various types of stars.

d      whether stars are in a spiral arm at them moment.

e       the probability that carbon-based life will develop if the right conditions occur.

 

 

17        Among other considerations elliptical galaxies differ from spiral galaxies in that spirals:

 

a       have a much wider mass range.

b      have interstellar gas and dust.

c       are composed generally population II objects.

d      are all very old.

e       are much brighter on the average than  the brightest ellipticals.

 


18        Gravitational Lensing:

 

a       occurs when the gravitational field of a star is lens shaped.

b      is a valuable tool in determining the mass distribution of the intermediate object.

c       is a technique that can be used to magnify telescope images much more that is possible with optical imaging techniques.

d      has been clearly detected in some quasar images.

e       has helped to characterize the dark matter distributions around galaxies.

 

 

19        The Large Scale Structure of the Universe is best characterized as:

 

a       smooth and homogeneous on the scale of the distribution of superclusters of galaxies..

b      containing many large void regions.

c       having only rarely occurring galactic collisions (i.e. collisions of galaxies are relatively rare events).

d      not being affected very much by the so-called dark matter.

e       resembling a foam-like structure.

 

 

20.       Inflation during the Big Bang refers to:

 

a.     the rapid expansion that occurred when gravity separated from the other forces and briefly became repulsive.

b.     a process that can explain the current observation of the acceleration of the expansion.

c.     the general property of the Big Bang that refers to the expansion of the universe with time.

d.     the fact that at the earliest times before the inflation occurred we were in causal contact with a portion of the universe that extends far beyond the present known universe.

e.     the fact that the knowable universe is bigger than the known universe.

 

 

21.       The current evidence for the acceleration of the Universe Includes

 

a.     …the number and size of the giant black holes in the centers of galaxies.

b.     …the shift in the shape of the Hubble Law for times more recent than about 5 Billion Light-Years

c.     …the data from the “Supernova Project.”

d.     …the discovery of the existence of Dark Matter.

e.     …the observation that we seem to have less and less time to get things done….

 

 

22.       Dark Energy:

 

a.     …has been postulated to be responsible for the acceleration of the Universe’s expansion.

b.     …is possibly due to quantum fluctuations of the vacuum.

c.     …is any form of energy that is not light.

d.     …is the same thing as dark matter according to Einstein’s Theory of Relativity.

e.     …could provide the matter needed to make the Universe exactly flat.

 

 

23.       Life on Earth:

 

a.     …generally is all based on the DNA molecule.

b.     …apparently started only about 500 Million years ago

c.     …began with the emergence of “extremophiles,” primitive bacteria-like cells that can exist in hostile environments.

d.     …existed as no more complex than single-celled bacteria for Billions of years

e.     …may be a rare example in the galaxy in the sense that complex life is very rare.

 

 

24.       Black Holes:

 

a.     may exist at the cores of all large galaxies.

b.     may have been created in the Big Bang in all sizes, including ones that are much smaller than the Sun’s mass.

c.     will have very strong tidal forces as one approaches the event horizon, for all black holes regardless of mass.

d.     Can be see directly by observing the light they all emit from their event horizons.

e.     are believe to be the source of ALL jet phenomenon seen in astronomical objects including stars.

 

 

25.       The greatest threats to the continued existence of the human species include:

 

a.     …our own rapid population growth.

b.     …Global Warming from the emission of green house gases.

c.     …new diseases that might wipe out all human beings.

d.     …the threat of invasion by a more advanced civilization and species from the stars.

e.     …the threat of major natural disasters like super-volcanoes and asteroid or comet impacts.