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A neutron star is

the remains of a star that died in a massive star supernova (if no black hole was created)

Based on current understanding, the minimum mass of a black hole that forms during a massive star supernova is roughly

3 solar masses

What do we mean by the singularity of a black hole?

It is the center of the black hole, a place of infinite density where the known laws of physics cannot describe the conditions.

ased on current evidence, which of the following statements about gamma ray bursts is true?

All those that we have detected occurred in distant galaxies

This series of images shows the pulsar at the center of the Crab Nebula looking bright every 0.033 second. Based on these data and current theory of pulsars, what can we conclude?

The pulsar is a neutron star that makes one full rotation every 0.033 second

Which of the following statements about degeneracy pressure is not true?

Degeneracy pressure can arise only from interactions among electrons

The white dwarf that remains when our Sun dies will be mostly made of

carbon

According to present understanding, a nova is caused by

hydrogen fusion on the surface of a white dwarf

Will our Sun ever undergo a white dwarf supernova explosion? Why or why not?

No, because it is not orbited by another star.

Each Voyager spacecraft carries a "postcard" designed to be understandable to any aliens that might someday encounter it. On the "postcard," scientists pinpointed the location of Earth by triangulating it between pulsars. Why did the scientists choose pulsars rather than some other type of star?

Pulsars are easy to identify by their almost perfectly steady periods of pulsation.

How does an accretion disk around a neutron star differ from an accretion disk around a white dwarf?

The accretion disk around a neutron star is much hotter and emits higher-energy radiation.

Which of statement below about black holes is not true?

A spaceship passing near a 10 solar mass black hole is much more likely to be destroyed than a spaceship passing at the same distance from the center of a 10 solar mass main-sequence star.

When we see X rays from an accretion disk in a binary system, we can't immediately tell whether the accretion disk surrounds a neutron star or a black hole. Suppose we then observe each of the following phenomena in this system. Which one would rule out the possibility of a black hole?

intense X-ray bursts

Which of the following statements about gamma ray bursts is not true?

he events responsible for gamma ray bursts apparently produce only gamma rays, and no other light that we can hope to detect.

Imagine an advanced civilization living on a planet orbiting at a distance of 10 AU (1.5 billion kilometers) from a close binary star system that consists of a 15 MSun red giant star and a 10 MSun black hole. The black hole is surrounded by an accretion disk. Sometime within the next million years or so, the civilization's planet is likely to be doomed because

he red giant will probably supernova within the next million years

Consider again the civilization described in the previous question. (They live on a planet orbiting 10 AU from a close binary star system that consists of a 15 MSun red giant star and a 10 MSun black hole surrounded by an accretion disk.) Through a bizarre (and scientifically unexplainable) fluctuation in the space-time continuum, a copy of a book from that civilization arrives on your desk; it is entitled Iguoonos: How We Evolved. In the first chapter, you learn that these beings evolved from organisms that lived 5 billion years ago. Which of the following statements should you expect to find as you continue to read this book?

hey evolved on a different planet in a different star system, and moved to their current location.

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