Fall 2000 ASTR 1120-001 Quiz 3

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  1. Which of the following is false? The stars in a star cluster have almost the same:
    (a) position on the sky; (b) distance; (c) age; (d) initial composition; (e) mass.

  2. The Hertzsprung-Russell diagram of the Pleiades contains lots of hot main sequence stars but no red giants, whereas the Hertzsprung-Russell diagram of the globular cluster M13 in Hercules contains lots of red giants but no hot main sequence stars. Therefore:
    (a) the stars in M13 are more luminous; (b) M13 formed less massive stars; (c) M13 is much younger; (d) M13 is much older; (e) M13 is much closer.

  3. Which of the following is false? Gravitational energy:
    (a) heats protostars to the point where they can ignite hydrogen; (b) is what powers main sequence stars like the Sun; (c) causes a star to contract and heat up when it has exhausted hydrogen at its center; (d) powers a core-collapse supernova; (e) heats an accretion disk surrounding a black hole to the point where it emits x-rays.

  4. The radius of a star in the Hertzsprung-Russell diagram can be inferred:
    (a) from its parallax; (b) from its apparent magnitude; (c) from Wien's Law, l T = 0.0029 m K; (d) from measurements of its mass, if the star is in a binary system; (e) from the Stefan-Boltzmann law, L = 4 p R2 s T4.

  5. Eddington explained the main sequence as a sequence of stars of different:
    (a) apparent magnitude; (b) distance; (c) age; (d) initial composition; (e) mass.

  6. Stars evolve off the main sequence because:
    (a) they exhaust hydrogen at their center and form a helium core; (b) the core becomes electron degenerate; (c) the core collapses and the star goes supernova; (d) they develop a very strong wind; (e) it's not true: stars evolve along the main sequence, not off it.

  7. `Planetary nebulae' were so named by William Herschel in the 18th century. We now know that a planetary nebula is:
    (a) a disk of gas and dust that will eventually form planets; (b) a cloud of gas and dust surrounding a planet; (c) a ring of glowing gas which is the blown off envelope of a red giant star; (d) the expanding debris from a supernova; (e) a galaxy.

  8. Which of the following is false? According to quantum mechanics, electrons:
    (a) have a frequency, so they know about time; (b) have a wavelength, so they know about space; (c) have a spin, so they know about direction in space; (d) travel at the speed of light; (e) obey an exclusion principle.

  9. Which of following statements about electron degeneracy is false:
    (a) white dwarfs are held up by electron degeneracy pressure; (b) the outer envelope of red giant stars is electron degenerate; (c) electron degeneracy pressure arises from the quantum nature of electrons ¾ they cannot be pushed together closer than a wavelength; (d) the temperature of electron degenerate matter can be low even though the electrons are quite energetic; (e) the outer electrons of atoms in metals at room temperature are degenerate, accounting for their high conductivity and reflectivity?

  10. When helium eventually ignites in the core of a star of about the mass of the Sun, it ignites explosively, producing a `helium flash'. The helium burning is explosive because:
    (a) the helium core is supported by electron degeneracy pressure, so the temperature skyrockets without causing the core to expand and quench; (b) helium contains much more nuclear energy than hydrogen; (c) the helium core collapses, releasing gravitational energy; (d) the star is unstable, and is observed as a Cepheid variable star; (e) it causes a Type II supernova.

  11. Which of the following statements about the Chandrasekhar Limit is false:
    (a) the Chandrasekhar Limit is the maximum mass of a white dwarf star; (b) the Chandrasekhar Limit is the maximum mass of a main sequence star; (c) the Chandrasekhar limit is about 1.4 solar masses; (d) a Type II supernova results when the iron core of a massive star exceeds the Chandrasekhar limit; (e) a Type Ia supernova results when a white dwarf accreting in a binary system reaches the Chandrasekhar limit?

  12. A Type II supernova follows the collapse of the iron core of a massive star. Why iron?
    (a) Iron is a particularly heavy element; (b) Iron contains a large amount of nuclear energy; (c) Iron contains no nuclear energy ¾ it is the most tightly bound of all nuclei; (d) Iron has strong magnetic properties; (e) Iron is radioactive.