Fall 2000 ASTR 1120-001 Quiz 3
Choose the single best answer and enter it on your scantron form.
Be sure to fill in your
name and
student number.
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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.
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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.
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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.
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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.
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Eddington explained the main sequence as a sequence of stars of different:
(a) apparent magnitude;
(b) distance;
(c) age;
(d) initial composition;
(e) mass.
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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.
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`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.
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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.
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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?
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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.
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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?
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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.