Form 1                                                                                                                                               Dr. Pinsky

Spring 2004

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.  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.             On an HR diagram:


a.       Écooler stars are generally plotted lower on the diagram than hotter stars.

b.       Éa lower luminosity star can never be appear higher up anywhere on the HR diagram with respect to the vertical axis than any star with a higher luminosity.

c.       ...the horizontal axis can be plotted as temperature.

d.       ...the vertical axis can be plotted in spectral types.

e.       Éany star that is generally both above and to the right of another star must always be the larger of the two stars.


 2.           Concerning stellar evolution:


a.       All stars less massive than the Sun generally evolve slower than the Sun as they initially evolve towards the ZAMS.

b.       T-Tauri variables are generally thought to be examples of Pre-ZAMS phenomena.

c.       all hydrogen "burning" concludes in the central-most core in the starŐs interior once a star leaves the main sequence.

d.       all observed variable stars are in a post main sequence phase.

e.       stars are always hotter at their surface when they "Helium Flash" than when they first left the main sequence.


 3.           Along the main sequence (for main sequence stars):


a.       All stars with a surface temperature substantially greater than the SunŐs have faster rates of evolution.

b.       All stars with a surface temperature substantially less than the SunŐs have masses that are less than the SunŐs as well.

c.       All stars are "burning" hydrogen in their central-most cores.

d.       All stars with a substantially greater luminosity than the SunŐs will have greater total main sequence lifetimes as well.

e.       The numbers of main sequence stars are distributed roughly equally both above and below the ZAMS (Zero Age Main Sequence) at each point along the main sequence.


4.             Our present theory of the Sun's internal structure is in some significant way based on our knowledge of:


a.       Éthe oldest biological growth records on earth being used to determine the constancy of the SunŐs luminosity over the largest part of itsŐ prior main sequence lifetime.

b.       Éthe fact that Jupiter has a composition thought to be identical to the Sun's.

c.       Éthe length of time it takes the Jupiter to orbit once around the sun to determine the SunŐs angular momentum.

d.       Éthe spectrum of the light coming from the Sun to determine the details of the SunŐs composition at its outer surface.

e.       Éthe period and semi-major axis of the earth's orbit to determine the SunŐs mass.

5.             Neutron stars:


a.       Édo not collapse further because electrons are fermions and they can become degenerate.

b.       Éare typically only about 10,000 miles across (~the size of the Earth).

c.          are thought to be the explanation for pulsars in many cases.

d.       Éare all thought to be remnants of supernovae.

e.       Éall have masses greater than the SunŐs.


 6.           Supernovae:


a.       Éresult, at least sometimes, in the formation of white dwarfs.

b.       Érelease most of their energy in the form of neutrinos.

c.       Éfor a few seconds, have a net luminosity that outshines the rest of the visible universe combined.

d.       Écan occur for white dwarfs in a binary system when it gets mass dumped on it by a companion star.

e.       Éhave progenitors which are always red giants (the star that becomes a supernova was a red giant just before that) for both Type I and Type II Supernovae.


 7.           The fundamental postulates of Special Relativity include or imply:


a.       clocks appear to run slower to an observer when the observer in question is fixed and the clock is moving, but not when the clock is fixed and that the observer in question is moving.

b.       the laws of physics do not depend upon the frame of the observer so long as it is an inertial frame of reference.

c.       distant objects will appear to be closer to a person moving towards them than they do to a person who is at rest with respect to the distant object and is being passed at that moment by the moving observer..

d.       light appears to move at the same speed in a vacuum as measured by all observers who are in inertial frames of reference.

e.       information can never be transmitted in the form of light.



 8.           For Black Holes:


a.       the phase "Black holes have no hair" refers to the idea that black holes can be differentiated only by mass, charge, and angular momentum.

b.       they always occur at the end of a starŐs life when more than ~1.2 solar masses remain in the core.

c.       there will be very strong tidal forces as one approaches the event horizon, at least for stellar sized black holes.

d.       they are typically identified by studying the emissions from the matter being accreted in disks close to the event horizon.

e.       would look like a giant whirlpool funnel in space.


 9.           Concerning the Space Time Diagram:


a.       you can always choose to stay at here-now without moving since that clearly is slower than the speed of light.

b.       at here-now you can only affect events that will occur in your future.

c.       elsewhere is not in our universe.

d.       as you move into your future some of what was in elsewhere can become part of your past at your new here-now, but parts of elsewhere can never become part of your future.

e.       the future and past are indistinguishable.


10.          General Relativity:


a.       is EinsteinŐs theory that gravity is due to the effect that the local energy density has on the geometry of space-time.

b.       still assumes that light moves in ŇstraightÓ lines, but predicts that the straight lines are bent.

c.       predicted neutron stars long before there was any evidence that they actually existed.

d.       Has been used to show how all of the laws of physics can be interpreted as simple geometric effects.

e.       allows the other forces to remain, but treats gravity as not being a force.

11.          The sunspot cycle:


a.       is a result of the Sun's periodic magnetic field reversals and the winding up of the magnetic field due to the SunŐs differential rotation.

b.       has been observed closely for only the last 100 years.

c.       can vary considerably in the total number of spots from one cycle to the next.

d.       actually requires about 22 years for the total true cycle period.

e.       is basically confined entirely to the SunŐs photosphere.


12.          The giant branch on an HR diagram:


a.       is located strictly above and to the right of the main sequence for both Population I and II stars.

b.       contains stars whose surface temperatures are all higher than the sun's.

c.       contains all of the red stars on the HR diagram.

d.       has stars that are all burning helium somewhere inside.

e.       may also contain many very bright blue stars.


13.          Pre-T-Tauri stars:


a.       appear first in the UV wavelengths at the extreme lower right hand edge of the HR diagram.

b.       have not yet reached the main sequence.

c.       also proceed through the RR-Lyrae variable stage prior to reaching the main sequence.

d.       all known present examples in the Milky Way are Population I (high heavy element abundance) type stars.

e.       generally slow their rate of contraction because of radiation flow outward from heating due to their gravitational contraction.


14.          Brown Dwarfs:


a.       are plotted at the extreme lower left-hand corner of an HR diagram.

b.       are all main sequence stars.

c.       are actually Ňfailed stars.Ó

d.       include Jupiter.

e.       are all thought to be the final evolutionary state of the lowest mass Main Sequence stars.


15.          Population II stars in our galaxy:


a.       generally are all very young.

b.       have roughly the same age distribution as Population I stars.

c.       contain a slightly larger fraction of their total mass as Hydrogen than do Population I stars.

d.       cannot participate readily in the C-N-O process even when they have sufficient mass.

e.       have HR diagrams that are generally identical to those of Population I stars.


16.                With regard to the Sun's atmospheric layers:


a.       the chromosphere lies directly above the photosphere.

b.       the upper boundary of the photoshpere is cooler than its lower boundary.

c.       they each have compositions that are similar to the air in this room.

d.       the photosphere is the region where 99% of the total light we see is emitted.

e.       the maximum temperature that occurs in each successive layer increases as one moves outward from the surface of the Sun.


17.          Fermions:


a.       Obey the Exclusion Principle.

b.       are never conserved by type.

c.       are the fundamental Ňbuilding blocksÓ of our universe.

d.       are all electrically charged.

e.       Obey the Uncertainty Principle.

18.          Concerning the Solar Neutrino Experiment that was done in the South Dakota mine, which of the following are true:


a.       the detector contained common soap-like laundry detergent as a source of neutrinos.

b.       it required a deep mine so that it is very dark and no sunlight can get in.

c.       it found too few neutrinos when compared with theoretical predictions.

d.       detected neutrinos by looking for 37Ar produced as a result of neutrino interactions.

e.       it attempted to "detect" neutrinos coming directly from the surface of the Sun.


19.          Cepheid variable stars:


a.       are variable stars with an average luminosity about the same as the SunŐs.

b.       have a rapidly varying energy source in their cores which cause the variation in the luminosity.

c.       reach the most dim point in their light curve when their atmospheres are the most contracted.

d.       are all main sequence stars.

e.       tend to have period-luminosity relationships that make them very useful as distance indicators.


20.          During post main sequence evolution:


a.       elements heavier than helium can be produced.

b.       the remaining lifetime is much shorter than the same star's main sequence lifetime had been.

c.       all stars will become extreme Population I stars in their surface spectrum.

d.       some stars continue to burn hydrogen in their innermost cores.

e.       all stars tend to increase their masses slightly.


21.          Fusion:


a.       when it results in the binding of previously unbound objects it must always be accompanied by a release of energy.

b.       refers to either the putting together of small objects or the breaking apart of big ones.

c.       results in a net decrease in the total mass if the resulting object is more tightly bound than the prior objects might have been.

d.       has never occurred on or near the earth, but only in the sun's core.

e.       increases the net amount of energy in the universe.


22.          Nucleosynthesis (fusion of smaller nuclei into larger ones) in stars:


a.       Tends to result in the production of the Uranium nuclei on the periodic table over Lead nuclei.

b.       Releases most of the energy in the form of neutrinos during the synthesis of the smaller nuclei.

c.       can release net energy all the way up to Uranium (U, Atomic Number = 92) nuclei.

d.       is occuring in the core of an isolated white dwarf.

e.       Produced all of the elements in your body heavier than hydrogenÉ


23.          Concerning the SunŐs interior


a.       Energy is transported principally via radiation in the region just below the visible surface.

b.       Energy is transported via radiation in the Convective Zone.

c.       The Radiative Zone is hotter and denser than the Convective Zone.

d.       The net luminosity of the core is essentially the same as that at the SunŐs surface.

e.       We cannot see any light coming directly from the interior, (by definition).