Question 1

What is the difference between a normal pulsar, which emits radiation in the radio range, and a pulsating X-ray source?

Accepted Answer

A)  A pulsating X-ray source combines the characteristics of an ordinary pulsar and a variable star. The surface pulsates in and out creating a pulsating source. 
B)  A pulsating X-ray source is a binary system of two pulsars in very rapid rotation around one another. One sees the interference pattern of the two pulsar beams as a pulsating X-ray jet. 
C)  A pulsating X-ray source is an ordinary pulsar, but occasionally, when the neutron star experiences a glitch and the crust cracks, the hot interior is exposed and emits an intense beam of X-rays. 
D)  A pulsating X-ray source is a pulsar with a binary companion. Matter pulled off the companion spirals along the intense magnetic field of the pulsar, and its interaction with the surface produces X-ray jets. 
A)  A pulsating X-ray source combines the characteristics of an ordinary pulsar and a variable star. The surface pulsates in and out creating a pulsating source. 
B)  A pulsating X-ray source is a binary system of two pulsars in very rapid rotation around one another. One sees the interference pattern of the two pulsar beams as a pulsating X-ray jet. 
C)  A pulsating X-ray source is an ordinary pulsar, but occasionally, when the neutron star experiences a glitch and the crust cracks, the hot interior is exposed and emits an intense beam of X-rays. 
D)  A pulsating X-ray source is a pulsar with a binary companion. Matter pulled off the companion spirals along the intense magnetic field of the pulsar, and its interaction with the surface produces X-ray jets.

Question 2

Aside from an atmosphere, the outermost layer of a neutron star is believed to consist of

Accepted Answer

A)  a dense gas consisting mostly of neutrons. 
B)  a molten ocean of heavy elements such as iron, neon, and magnesium. 
C)  a solid crust. 
D)  superfluid neutrons. 
A)  a dense gas consisting mostly of neutrons. 
B)  a molten ocean of heavy elements such as iron, neon, and magnesium. 
C)  a solid crust. 
D)  superfluid neutrons.

Question 3

Nuclear fusion reactions of helium produce primarily

Accepted Answer

A)  nitrogen and neon nuclei. 
B)  iron nuclei. 
C)  beryllium and lithium nuclei. 
D)  carbon and oxygen nuclei. 
A)  nitrogen and neon nuclei. 
B)  iron nuclei. 
C)  beryllium and lithium nuclei. 
D)  carbon and oxygen nuclei.

Question 4

What is the difference between a "helium flash" and a "helium shell flash"?

Accepted Answer

A)  A helium flash occurs when the core becomes supported by electron-degeneracy pressure; a helium shell flash occurs when the helium shell becomes supported by electron-degeneracy pressure. 
B)  All stars with mass less than 8 times the mass of the Sun undergo a helium flash, but only those between 2 and 8 times the mass of the Sun undergo a helium shell flash. 
C)  A helium flash occurs just once; a helium shell flash can repeat many times. 
D)  A helium flash results in a supernova; a helium shell flash results on a planetary nebula. 
A)  A helium flash occurs when the core becomes supported by electron-degeneracy pressure; a helium shell flash occurs when the helium shell becomes supported by electron-degeneracy pressure. 
B)  All stars with mass less than 8 times the mass of the Sun undergo a helium flash, but only those between 2 and 8 times the mass of the Sun undergo a helium shell flash. 
C)  A helium flash occurs just once; a helium shell flash can repeat many times. 
D)  A helium flash results in a supernova; a helium shell flash results on a planetary nebula.

Question 5

The diameter of a typical neutron star of 2 solar masses is predicted to be approximately

Accepted Answer

A)  1 km. 
B)  that of a small city, about 20 kilometers. 
C)  that of the Sun. 
D)  that of Earth, 12,800 km. 
A)  1 km. 
B)  that of a small city, about 20 kilometers. 
C)  that of the Sun. 
D)  that of Earth, 12,800 km.

Question 6

A star of 25 solar masses spends roughly what percentage of its life as a main-sequence star?

Accepted Answer

A)  about 7% 
B)  very little, less than 1% 
C)  93% 
D)  58% 
A)  about 7% 
B)  very little, less than 1% 
C)  93% 
D)  58%

Question 7

What are "thermal pulses"?

Accepted Answer

A)  These are the loops formed on the H-R diagram as the evolutionary tracks of low-mass stars move beyond the planetary nebula stage. 
B)  These are the pulses of radiation emitted during helium shell flashes. 
C)  This is another name for the high luminosity pulses of radiation emitted periodically by variable stars. 
D)  This is the burst of radiation given off during a nova. 
A)  These are the loops formed on the H-R diagram as the evolutionary tracks of low-mass stars move beyond the planetary nebula stage. 
B)  These are the pulses of radiation emitted during helium shell flashes. 
C)  This is another name for the high luminosity pulses of radiation emitted periodically by variable stars. 
D)  This is the burst of radiation given off during a nova.

Question 8

Which of these important components does a planetary nebula contribute to the interstellar medium?

Accepted Answer

A)  molecules such as NH3 and CH4, which contribute to giant molecular clouds 
B)  UV light photoionizes hydrogen. The hydrogen, on recombination, produces the red Balmer-$\alpha$light by which interstellar emission nebulae are seen. 
C)  rotational motion from the original star, which serves to concentrate interstellar matter into new stars and planetary systems 
D)  nuclei of moderately heavy elements, major components of planets such as Earth. 
A)  molecules such as NH3 and CH4, which contribute to giant molecular clouds 
B)  UV light photoionizes hydrogen. The hydrogen, on recombination, produces the red Balmer-$\alpha$light by which interstellar emission nebulae are seen. 
C)  rotational motion from the original star, which serves to concentrate interstellar matter into new stars and planetary systems 
D)  nuclei of moderately heavy elements, major components of planets such as Earth.

Question 9

Pulsating X-ray sources are believed to be

Accepted Answer

A)  white dwarf stars with intense magnetic fields; the X-rays are generated by flares like those on the Sun but much stronger. 
B)  spinning neutron stars in binary systems, emitting X-rays because of mass transfer onto the neutron star from its normal companion. 
C)  the same as regular (optical) pulsars but observed in X-rays. 
D)  black holes in binary systems, with an accretion disk around the black hole emitting X-rays. 
A)  white dwarf stars with intense magnetic fields; the X-rays are generated by flares like those on the Sun but much stronger. 
B)  spinning neutron stars in binary systems, emitting X-rays because of mass transfer onto the neutron star from its normal companion. 
C)  the same as regular (optical) pulsars but observed in X-rays. 
D)  black holes in binary systems, with an accretion disk around the black hole emitting X-rays.

Question 10

MOST supernova remnants can be observed only at nonvisible wavelengths. Explain.

Accepted Answer

A)  Supernova remnants are too cool to produce radiation at visible wavelengths. 
B)  Supernova remnants are too hot to produce radiation at visible wavelengths. 
C)  Visible wavelengths are produced by supernova remnants but they are blocked by the interstellar medium. 
D)  All the visible wavelengths are Doppler shifted to infrared because all the supernova remnants are moving away from Earth at high speeds. 
A)  Supernova remnants are too cool to produce radiation at visible wavelengths. 
B)  Supernova remnants are too hot to produce radiation at visible wavelengths. 
C)  Visible wavelengths are produced by supernova remnants but they are blocked by the interstellar medium. 
D)  All the visible wavelengths are Doppler shifted to infrared because all the supernova remnants are moving away from Earth at high speeds.

Question 11

A white dwarf star is about the same size as

Accepted Answer

A)  the Sun. 
B)  Earth. 
C)  the total solar system. 
D)  a major city. 
A)  the Sun. 
B)  Earth. 
C)  the total solar system. 
D)  a major city.

Question 12

The MOST recent supernova explosion known to have occurred in the Milky Way Galaxy

Accepted Answer

A)  was seen in 1987 (supernova 1987
A) . 
B)  created the Gum Nebula. 
C)  gave rise to the Crab Nebula. 
D)  created the supernova remnant Cassiopeia A. 
A)  was seen in 1987 (supernova 1987
A) . 
B)  created the Gum Nebula. 
C)  gave rise to the Crab Nebula. 
D)  created the supernova remnant Cassiopeia A.

Question 13

The final remnant of the evolution of a red giant star that has ejected a planetary nebula is a

Accepted Answer

A)  protostar. 
B)  blue supergiant. 
C)  white dwarf star. 
D)  supernova. 
A)  protostar. 
B)  blue supergiant. 
C)  white dwarf star. 
D)  supernova.

Question 14

In a star's evolutionary life, the asymptotic giant branch (AGB) is the

Accepted Answer

A)  helium core fusion phase. 
B)  pre-main-sequence core hydrogen fusion phase. 
C)  hydrogen shell fusion phase prior to helium ignition in the core. 
D)  helium shell fusion phase. 
A)  helium core fusion phase. 
B)  pre-main-sequence core hydrogen fusion phase. 
C)  hydrogen shell fusion phase prior to helium ignition in the core. 
D)  helium shell fusion phase.

Question 15

A sequence of thermonuclear fusion processes inside massive stars can continue to transform the nuclei of elements such as carbon and oxygen into heavier nuclei and also generate excess energy up to a limit beyond which no further energy-producing reactions can occur. The element that is produced when this limit is reached is

Accepted Answer

A)  oxygen. 
B)  iron. 
C)  silicon. 
D)  uranium. 
A)  oxygen. 
B)  iron. 
C)  silicon. 
D)  uranium.

Question 16

Stars that have ejected a planetary nebula go on to become

Accepted Answer

A)  red giants. 
B)  supernovae. 
C)  protostars. 
D)  white dwarfs. 
A)  red giants. 
B)  supernovae. 
C)  protostars. 
D)  white dwarfs.

Question 17

Where are supernova explosions MOST likely to occur?

Accepted Answer

A)  only in other galaxies with active nuclei 
B)  in the globular clusters surrounding the Milky Way Galaxy 
C)  in the plane of the Milky Way Galaxy 
D)  only in irregular galaxies, like the Large Magellanic Cloud, where star formation remains an ongoing process 
A)  only in other galaxies with active nuclei 
B)  in the globular clusters surrounding the Milky Way Galaxy 
C)  in the plane of the Milky Way Galaxy 
D)  only in irregular galaxies, like the Large Magellanic Cloud, where star formation remains an ongoing process

Question 18

The temperature of the hot spots caused by the impact of transferred matter onto the surface of a pulsar can be 108 K. What is the peak wavelength in the blackbody spectrum of such a spot, and in what range of the electromagnetic spectrum does it occur?

Accepted Answer

A)  2.9 *10-11 nm; gamma ray 
B)  2.9 *10-2 nm; X-ray 
C)  290 nm; ultraviolet 
D)  2.9 *107 nm; radio 
A)  2.9 *10-11 nm; gamma ray 
B)  2.9 *10-2 nm; X-ray 
C)  290 nm; ultraviolet 
D)  2.9 *107 nm; radio

Question 19

Which observation has provided the MOST direct evidence that Type II supernovae are caused by the collapse of the core of a massive star?

Accepted Answer

A)  detection of high-energy X-rays from the Crab supernova remnant 
B)  detection of iron in the Cassiopeia A supernova remnant 
C)  detection of neutrinos from supernova 1987A 
D)  discovery of cosmic rays 
A)  detection of high-energy X-rays from the Crab supernova remnant 
B)  detection of iron in the Cassiopeia A supernova remnant 
C)  detection of neutrinos from supernova 1987A 
D)  discovery of cosmic rays

Question 20

An old high-mass star can have a number of shells (hydrogen, helium, carbon, neon, oxygen, silicon) plus an iron core. Fusion generally takes place in all these regions EXCEPT the

Accepted Answer

A)  hydrogen shell. 
B)  helium shell. 
C)  silicon shell. 
D)  iron core. 
A)  hydrogen shell. 
B)  helium shell. 
C)  silicon shell. 
D)  iron core.

What is the difference between a normal pulsar, which emits radiation in the radio range, and a pulsating X-ray source?

Aside from an atmosphere, the outermost layer of a neutron star is believed to consist of

Nuclear fusion reactions of helium produce primarily

What is the difference between a "helium flash" and a "helium shell flash"?

The diameter of a typical neutron star of 2 solar masses is predicted to be approximately

A star of 25 solar masses spends roughly what percentage of its life as a main-sequence star?

What are "thermal pulses"?

Which of these important components does a planetary nebula contribute to the interstellar medium?

Pulsating X-ray sources are believed to be

MOST supernova remnants can be observed only at nonvisible wavelengths. Explain.

A white dwarf star is about the same size as

The MOST recent supernova explosion known to have occurred in the Milky Way Galaxy

The final remnant of the evolution of a red giant star that has ejected a planetary nebula is a

In a star's evolutionary life, the asymptotic giant branch (AGB) is the

Stars that have ejected a planetary nebula go on to become

Where are supernova explosions MOST likely to occur?

The temperature of the hot spots caused by the impact of transferred matter onto the surface of a pulsar can be 10⁸ K. What is the peak wavelength in the blackbody spectrum of such a spot, and in what range of the electromagnetic spectrum does it occur?

Which observation has provided the MOST direct evidence that Type II supernovae are caused by the collapse of the core of a massive star?

An old high-mass star can have a number of shells (hydrogen, helium, carbon, neon, oxygen, silicon) plus an iron core. Fusion generally takes place in all these regions EXCEPT the

Discovering the Night Sky

Gravitation and the Motion of the Planets

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Formation of the Solar System

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The Sun: Our Extraordinary Star

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Black Holes: Matters of Gravity

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Exam 14: The Death of Stars

What is the difference between a normal pulsar, which emits radiation in the radio range, and a pulsating X-ray source?

Aside from an atmosphere, the outermost layer of a neutron star is believed to consist of

Nuclear fusion reactions of helium produce primarily

What is the difference between a "helium flash" and a "helium shell flash"?

The diameter of a typical neutron star of 2 solar masses is predicted to be approximately

A star of 25 solar masses spends roughly what percentage of its life as a main-sequence star?

What are "thermal pulses"?

Which of these important components does a planetary nebula contribute to the interstellar medium?

Pulsating X-ray sources are believed to be

MOST supernova remnants can be observed only at nonvisible wavelengths. Explain.

A white dwarf star is about the same size as

The MOST recent supernova explosion known to have occurred in the Milky Way Galaxy

The final remnant of the evolution of a red giant star that has ejected a planetary nebula is a

In a star's evolutionary life, the asymptotic giant branch (AGB) is the

Stars that have ejected a planetary nebula go on to become

Where are supernova explosions MOST likely to occur?

The temperature of the hot spots caused by the impact of transferred matter onto the surface of a pulsar can be 108 K. What is the peak wavelength in the blackbody spectrum of such a spot, and in what range of the electromagnetic spectrum does it occur?

Which observation has provided the MOST direct evidence that Type II supernovae are caused by the collapse of the core of a massive star?

An old high-mass star can have a number of shells (hydrogen, helium, carbon, neon, oxygen, silicon) plus an iron core. Fusion generally takes place in all these regions EXCEPT the

Discovering the Night Sky

Gravitation and the Motion of the Planets

Light and Telescopes

Atomic Physics and Spectra

Exoplanets and the Formation of Planetary Systems

Formation of the Solar System

Earth and the Moon

The Other Terrestrial Planets

The Outer Planets

Vagabonds of the Solar System

The Sun: Our Extraordinary Star

Characterizing Stars

The Lives of Stars From Birth Through Middle Age

Black Holes: Matters of Gravity

The Milky Way Galaxy

Galaxies

Quasars and Other Active Galaxies

Cosmology

Astrobiology

Filters

The temperature of the hot spots caused by the impact of transferred matter onto the surface of a pulsar can be 10⁸ K. What is the peak wavelength in the blackbody spectrum of such a spot, and in what range of the electromagnetic spectrum does it occur?