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Exam 23: The Death of Stars

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Question 1

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What kind of telescope did Jocelyn Bell use to discover pul?sars in 1968?

A) visible light
B) radio
C) ultraviolet
D) x-ray
E) neutr?ino

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Question 2

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If observations of supernovae in other galaxies show that such an explosion happens in a spiral galaxy like the Milky Way on average every 25 to 100 years, why have astronomers on Earth not seen a supernova explosion in our Galaxy since 1604?

A) we have been very unlucky; there have been far fewer explosions than average recently
B) all the explosions happened in that part of the sky which is only visible from the Earth's southern hemisphere, and we do not have any large telescopes down there
C) the disk of our Galaxy contains a great deal of dust, which tends to block the light of supernova explosions from more distant parts of our Galaxy
D) most supernova explosions produce only high-energy gamma-rays and very little light
E) actually, there have been supernova explosions observed, but there is a government conspiracy to keep ordinary citizens from learning about them (just like the alien creatures that were in Roswell, New Mexico and Area 51)

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Question 3

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Which of the following is one reason we do not detect a pulsar in many remnants of supernova explosions?

Astronomers have discovered pulsars spinning 500 x per second or more. How do astronomers think pulsars got to be spinning so outrageously fast?

In a supernova like SN1987A, once the crisis of iron fusion has begun, roughly how long does it take the star's core to collapse?

Although centuries ago, astronomers thought that a nova was a new star, appearing for the first time in the heavens, today we know that it is:

Astronomer have concluded that pulsars are

When a single star with a mass equal to the Sun dies, it will become a

Which of the following statements about Supernova 1987A is FALSE?

A member of the college football team wants to weigh as much as possible. Assuming he could somehow survive on all of them, at the surface of which object would he weigh the most?

A white dwarf, compared to a main sequence star with the same mass, would always be:

Astronomers have long realized that supernovae -- when they explode -- give off an enormous amount of light. But observations of Supernova 1987A (in the Large Magellanic Cloud) revealed that the supernova gives off even more energy in another form? That form is:

A charming friend of yours who has been reading a little bit about astronomy accompanies you to the campus observatory and asks to see the kind of star that our Sun will ultimately become, long, long after it has turned into a white dwarf. Why is the astronomer on duty going to have a bit of a problem satisfying her request?

Your sweetheart gives you a piece of gold jewelry as a present to celebrate your passing your astronomy class. Where did the gold atoms in that gift originally come from (where were they most likely made) ?

Astronomers observe a young cluster of stars, where stars with three times the mass of the Sun are still on the main sequence of the H-R diagram. Yet the cluster contains two white dwarfs, each with a mass less than 1.4 times the mass of the Sun. If we can show that the white dwarfs are definitely part of the cluster, how can their presence so soon in the life of the cluster be explained?

Which of the following stages can only occur in the life of a low-mass star (whose final mass is less than 1.4 times the mass of the Sun) ?

Which of the following is NOT a result of supernova explosions?

Which of the following statements about the Crab Nebula is FALSE?

In the model that astronomers have developed for pulsars, why do they suggest that there must be two beams of energy coming from the pulsar?

A type Ia supernova involves the transfer of mass from one star to a companion white dwarf? Yet, in some cases, astronomers cannot locate a star near where they see Type Ia explosions. How do they explain the absence of a companion star?