29:50 Modern Astronomy
Third Hour Exam...Example
November 13, 2002
Una Salus Victis, Nullam Sperare Salutem
......Virgil, The Aeniad, Book II
Form A

1. The ultimate fate of the Sun is to become what type of astronomical object?
   (a) red dwarf
   (b) neutron star
   (c) white dwarf X
   (d) a UX UMa star
   (e) black hole
2. The primary difference in the evolutionary history of a star like the Sun ( a so-called low mass star) and a very massive star (say 25 solar masses) is
   (a) massive stars become black dwarfs whereas solar type stars become neutron stars.
   (b) massive stars never are found on the main sequence, whereas all low mass stars have this phase.
   (c) low mass stars are formed in molecular clouds whereas massive stars form in the open interstellar medium.
   (d) a star like the Sun will never leave the main sequence.
   (e) the massive star ends its life in a supernova explosion. X
3. What is the Main Sequence lifetime of the Sun?
   (a) 20 billion years
   (b) 10 billion years X
   (c) 200 billion years
   (d) 500 million years
   (e) 4314 years
4. The post main sequence phase of any star (low mass or high mass) involves one of the following processes somewhere in the star. Which is it?
   (a) The fusion of helium to form carbon in a process called the Triple Alpha process X
   (b) The fusion of hydrogen to form helium in the very center of the star
   (c) Direct conversion of matter and antimatter into energy
   (d) An accretion disk surrounding a massive black hole
   (e) A region in which the stellar matter is entirely formed of the element Dysprosium
5. In class I discussed a class of objects called neutron stars. What is the status of current astronomical knowledge regarding their existence (or nonexistence)?
   (a) The stars in the star cluster the Pleiades are neutron stars.
   (b) The star Persei (Algol) is one of the few known neutron stars.
   (c) Radio pulsars are neutron stars. X
   (d) Neutron stars are still highly speculative objects; there is considerable indirect evidence for their existence, but a definitive demonstration is not yet available.
   (e) Neutron stars have been found at the center of massive galaxies.
6. Which of the following statements gives a correct description of what we mean by stellar evolution?
   (a) Over a period of millions to billions of years, stars change in luminosity, surface temperature, and chemical composition. The rate and nature of these changes is determined by the stellar mass. X
   (b) Stellar evolution is similar to biological evolution. In different parts of the galaxy, stars have developed in entirely different ways and are described by quite different physical laws.
   (c) Stellar evolution refers only to the fact that we see different stars at different distances, and therefore different stages in their life. There is no evidence that stars significantly differ among each other.
   (d) The main factor which governs stellar evolution is the location in the galaxy where the star forms.
   (e) When evolution is outlawed, only outlaws will evolve!!!
7. In class I discussed the status of the search for stars similar to the Sun. Which of the following statements most accurately describes our knowledge of other stars like the Sun?
   (a) Astronomers have identified about 100 other stars similar to the Sun in terms of mass, surface temperature, luminosity, and age. They are classified into the categories of solar-type star, solar analog, and solar twin. X
   (b) As a result of the Chandra spacecraft, thousands of stars have been identified that are virtually identical to the Sun. They are grouped into categories of solar proxies and solar-sodales stars.
   (c) Astronomers are aware that there are other stars with similar surface temperatures and roughly similar luminosities to the Sun. The only cases in which an extensive comparison has been made is for the stars Ceti and Eridani.
   (d) The total number of stars known to be similar to the Sun is five. Spectral class G stars are common, but almost all of the ones known are giants and supergiants instead of main sequence stars.
   (e) Amazingly enough, the Sun appears to be virtually unique among stars. We know of very few, and maybe no other stars, which have approximately the same mass, temperature, and age of the Sun.
8. The most fundamental physical definition of a Black Hole is
   (a) An object which emits no light.
   (b) An object which is inside of its Schwarzschild Radius. X
   (c) An object whose angular momentum exceeds the Planck-Wheeler momentum.
   (d) A star which no longer produces nuclear fusion reactions.
   (e) An object in which the strong nuclear force overcome the repulsive force of electricity and magnetism.
9. Which of the following is considered by astronomers as adequate observational evidence for the existence of a Black Hole?
   (a) A star which emits less than 10 percent of the light of the Sun.
   (b) A binary star in which one of the objects is a degenerate object with a mass of 1.4 solar masses.
   (c) A star which emits less than 1 percent of the light of the Sun.
   (d) A binary star in which one of the objects is a degenerate object with a mass in excess of about 3 solar masses. X
   (e) A source of strong and variable X-ray emission.
10. General Relativity is
    (a) the current theory of the nature of electricity and magnetism.
    (b) the most exact known theory of gravity. X
    (c) a theory that tells us how electromagnetic radiation is produced by moving charges.
    (d) the statement that the results of physics experiments, and indeed the whole form of physical law, depend entirely on the observer.
    (e) the physical basis of Wien's Law.
11. The overall shape of the Milky Way galaxy is
    (a) a roughly spherical system.
    (b) a disk, with a diameter much larger than its thickness. X
    (c) a central spherical distribution, a gap, and then an annulus of stars with a radius of about 4.5 Megaparsecs.
    (d) a slightly flattened spheroid.
    (e) cylindrical, with the axis of the cylinder pointing toward the Coma cluster.
12. In what class of astronomical object would we place the Milky Way?
    (a) Spiral galaxy X
    (b) Elliptical galaxy
    (c) Irregular galaxy
    (d) Quasar
    (e) Planetary Nebula
13. Modern astronomy has identified the places where stars are formed, that is come into existence. These regions are identified with
    (a) the brightest stars in the galaxy.
    (b) the center of the galaxy.
    (c) the ``galactic halo'', from which stars settle into the disk of the Milky Way.
    (d) regions of the interstellar medium where no other stars have formed.
    (e) opaque clouds of molecular gas. X
    
14. The Sun obtains its energy from
    (a) nuclear fission reactions on the solar surface.
    (b) nuclear fusion reactions in its core. X
    (c) the conversion of gravitational potential energy to heat energy.
    (d) extremely explosive chemical reactions.
    (e) the process of magnetic reconnection.
    
15. Which of the following statements about gaseous matter between the stars is correct?
    (a) Gas containing complex molecules exists in dark clouds near young star clusters. X
    (b) Gas has never been detected in the interstellar medium despite extensive efforts.
    (c) All gas in the interstellar medium is subject to cosmic rays and ultraviolet light, and so is ionized and at extremely high temperatures.
    (d) The gas in the interstellar medium presents a conceptual difficulty, since its elemental composition is different than that of stars.
    (e) Gas existed in the galaxy early in the history of the universe, but was blown out in the first generation of star formation.
    
16. Based on your knowledge of astronomy, which of the following is an object which should not exist?
    (a) A Main Sequence star with five times the mass of the Sun which formed 10 billion years ago. X
    (b) A Main Sequence star with three times the mass of the Sun which is 500 million years old.
    (c) A star with 25 times the mass of the Sun.
    (d) A star with 5 times the mass of the Sun which is now a red supergiant.
    (e) A star with one half the mass of the Sun which formed ten billion years ago and is still a Main Sequence star.
    
17. Using the terminology introduced in class, what kind of star is the Sun?
    (a) a spectral class A Main Sequence star.
    (b) a spectral class G Main Sequence star. X
    (c) a spectral class M Main Sequence star.
    (d) a spectral class G Giant star.
    (e) a Neutron Star.
    
18. The Hertzsprung-Russell Diagram is a famous plot in which we plot one stellar property (the x axis) versus another stellar property (the y axis). Which two properties are plotted?
    (a) Absolute Magnitude versus distance
    (b) Absolute Magnitude versus Spectral Type X
    (c) Absolute Magnitude versus Apparent Magnitude
    (d) distance versus Spectral Type
    (e) Luminosity versus Absolute Magnitude
    
19. If you take the nearest 100 stars and sort them according to class, what will you find to be the most common type of star?
    (a) solar type star
    (b) spectral class A Main Sequence star
    (c) red giant
    (d) white dwarf
    (e) red dwarf X
    
20. Observations of binary stars are important in astronomy. What is the most important thing we learn from observations of binary stars?
    (a) the surface temperatures of stars
    (b) the energy source of stars
    (c) the masses of stars X
    (d) the distances of stars
    (e) the way stars evolve
    

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