Question 1

Star A has twice the parallax as Star B. Star A is
A)twice as far as Star B.
B)four times as far as Star B.
C)eight times as far as Star B.
D)half as far as Star B.
E)one fourth as far as Star B.

Accepted Answer

Parallax is inversely proportional to distance. If Star A has twice the parallax of Star B, it means Star A is half as far away as Star B.

Question 2

Which is the latest stage (of those given below) in the evolution of a star?
A)red giant
B)white dwarf
C)protostar
D)geodesic
E)supernova

Accepted Answer

A supernova is the latest stage listed, occurring after a star has exhausted its nuclear fuel and undergone a catastrophic explosion.

Question 3

One star has a surface temperature of 6000 K and another has a surface temperature of 7000 K. If the two stars have the same absolute luminosity, which star has the largest radius?
A)the star at 6000 K
B)the star at 7000 K
C)The two stars have the same radius.
D)Not enough information is given to determine.

Accepted Answer

According to the Stefan-Boltzmann Law, luminosity is proportional to the surface area and the fourth power of temperature. If both stars have the same luminosity, the cooler star (6000 K) must have a larger radius to compensate for its lower temperature.

Question 4

Which of the following is arranged from hottest surface temperature to coolest surface temperature?
A)white dwarf, red giant, the sun
B)white dwarf, the sun, red giant
C)the sun, red giant, white dwarf
D)red giant, the sun, white dwarf
E)red giant, white dwarf, the sun

Accepted Answer

White dwarfs have the hottest surface temperatures, followed by the Sun, and then red giants, which have cooler surface temperatures.

Question 5

Black holes
A)are holes in space, devoid of matter.
B)are predicted by Einstein's special theory of relativity.
C)are the collapsed remnant of stars.
D)cannot be detected in binary star systems.
E)are a violation of Einstein's general theory of relativity.

Accepted Answer

Black holes are formed from the remnants of massive stars that have collapsed under their own gravity after exhausting their nuclear fuel.

Question 6

The diameter of the Milky Way is 100,000 ly. This distance in SI units is A)5 x 10¹⁵ m. B)1 x 10²¹ m. C)4 x 10³⁰ m. D)3 x 10³⁶ m. E)2 x 10⁴² m.

Accepted Answer

1 light-year is approximately 9.461 x 10^15 meters. Therefore, 100,000 light-years is 100,000 x 9.461 x 10^15 meters, which equals approximately 9.461 x 10^20 meters, close to 1 x 10^21 meters.

Question 7

The Chandrasekhar limit of stellar mass (below which a star will collapse into a white dwarf) is, if the mass of our Sun is M, about
A)0.8 M.
B)1.2 M.
C)1.4 M.
D)1.9 M.
E)2.8 M.

Accepted Answer

The Chandrasekhar limit is approximately 1.4 times the mass of the Sun (1.4 M). This is the maximum mass a white dwarf star can have before it collapses under its own gravity to form a neutron star or black hole.

Question 8

A Hertzsprung-Russell diagram shows stars on a plot of
A)apparent brightness vs. temperature.
B)luminosity vs. temperature.
C)luminosity vs. distance.
D)magnitude vs. apparent brightness.
E)magnitude vs. distance.

Accepted Answer

The Hertzsprung-Russell diagram plots stars according to their luminosity and temperature, showing the relationship between these two properties.

Question 9

State Einstein's principle of equivalence.

Accepted Answer

The answer of State Einstein's principle of equivalence....

Question 10

When a distant source emits light of a particular wavelength in the visible, and the source is moving away from us, the color of the light appears to us to be shifted toward the
A)red end of the visible spectrum.
B)blue end of the visible spectrum.

Accepted Answer

This is known as redshift, and it occurs because as the source moves away from us, the wavelength of the light waves is stretched out, causing them to appear redder. The faster the source is moving away, the greater the redshift.

Question 11

In the standard model, about when after the Big Bang did the universe become transparent to radiation? A)10^-43 s B)10^-³⁵ s C)10³ s D)3 × 10⁵ y E)3 × 10⁶ y

Accepted Answer

The universe became transparent to radiation about 380,000 years after the Big Bang, when electrons and protons combined to form neutral hydrogen atoms, allowing photons to travel freely.

Question 12

The Schwarzschild radius of a black hole is that radial distance from the center of a sphere within which not even light can escape. It was first discovered mathematically by Schwarzschild in 1916 after Einstein published his general relativity theory. It can be calculated from a star's mass M as: R = 2GM/c². Take the radius of both stars A and B as the Schwarzschild radius. If the mass of star A is twice as much as the mass of star B, the average density of star A, compared to star B will be A)the same. B)twice as much. C)half as much. D)four times as much. E)one-fourth as much.

Accepted Answer

The Schwarzschild radius is proportional to the mass, so if star A has twice the mass of star B, its radius is also twice as large. Since volume scales with the cube of the radius, the volume of star A is 2^3 = 8 times that of star B. Therefore, the density, which is mass divided by volume, is 1/4 that of star B.

Question 13

Pulsars are rapidly spinning
A)regular stars like our Sun.
B)red giant stars.
C)neutron stars.
D)white dwarfs.
E)supernova.

Accepted Answer

Pulsars are a type of neutron star, which are the remnants of massive stars that have exploded in supernovae. They are incredibly dense and spin rapidly, emitting beams of radiation from their magnetic poles.

Question 14

The appearance of the great range of brightness among stars is due to
A)the differences in the amount of light different stars emit.
B)the differences in the distances of stars from us.
C)both of the given answers
D)none of the given answers

Accepted Answer

The brightness of stars as observed from Earth depends on both their intrinsic luminosity (the amount of light they emit) and their distance from us.

Question 15

Supernovas are thought to always result in
A)neutron stars.
B)red giant stars.
C)regular stars like our Sun.
D)white dwarfs.
E)black dwarfs.

Accepted Answer

Supernovas often result in neutron stars if the core remnant is between about 1.4 and 3 solar masses. If the remnant is more massive, it may become a black hole.

Question 16

If a galaxy is receding at 0.10 c, how far away is the galaxy if the Hubble parameter is 70 km/s/Mpc? A)1.4 × 10⁹ ly B)23 Mpc C)76 Mly D)7 Mpc E)1.4 × 10⁷ ly

Accepted Answer

The answer of If a galaxy is receding at 0.10...

Question 17

A white dwarf star with a mass equal to that of the Sun is about the size of
A)the Sun.
B)the Earth.
C)a basketball.
D)a baseball.
E)a golfball.

Accepted Answer

A white dwarf star with a mass similar to the Sun is about the size of the Earth due to its high density and compact nature.

Question 18

If a source of light is moving away at 10% the speed of light, its wavelength will
A)be lengthened by 22%.
B)be lengthened by 11%.
C)be shortened by 22%.
D)be shortened by 11%.
E)remain unchanged.

Accepted Answer

When a source of light moves away from an observer, the light experiences a redshift, meaning its wavelength is lengthened. The relativistic Doppler effect formula shows that at 10% the speed of light, the wavelength is lengthened by approximately 11%.

Question 19

Four different main-sequence stars are colored blue, orange, red, and yellow. What is their rank from coolest to hottest?
A)blue, yellow, orange, red
B)blue, orange, red, yellow
C)orange, blue, yellow, red
D)red, orange, yellow, blue
E)red, yellow, orange, blue

Accepted Answer

Main-sequence stars are ranked by temperature from coolest to hottest as red, orange, yellow, and blue.

Question 20

The cosmic background radiation corresponds to a temperature of about
A)1.4 K.
B)2.7 K.
C)3.0 K.
D)3.3 K.
E)3.6 K.

Accepted Answer

The cosmic microwave background radiation corresponds to a temperature of approximately 2.7 K, which is the remnant heat from the Big Bang.

Quiz 44: Astrophysics and Cosmology

Star A has twice the parallax as Star B. Star A is

Which is the latest stage (of those given below) in the evolution of a star?

One star has a surface temperature of 6000 K and another has a surface temperature of 7000 K. If the two stars have the same absolute luminosity, which star has the largest radius?

Which of the following is arranged from hottest surface temperature to coolest surface temperature?

Black holes

The diameter of the Milky Way is 100,000 ly. This distance in SI units is

The Chandrasekhar limit of stellar mass (below which a star will collapse into a white dwarf) is, if the mass of our Sun is M, about

A Hertzsprung-Russell diagram shows stars on a plot of

State Einstein's principle of equivalence.

When a distant source emits light of a particular wavelength in the visible, and the source is moving away from us, the color of the light appears to us to be shifted toward the

In the standard model, about when after the Big Bang did the universe become transparent to radiation?

Pulsars are rapidly spinning

The appearance of the great range of brightness among stars is due to

Supernovas are thought to always result in

If a galaxy is receding at 0.10 c, how far away is the galaxy if the Hubble parameter is 70 km/s/Mpc?

A white dwarf star with a mass equal to that of the Sun is about the size of

If a source of light is moving away at 10% the speed of light, its wavelength will

Four different main-sequence stars are colored blue, orange, red, and yellow. What is their rank from coolest to hottest?

The cosmic background radiation corresponds to a temperature of about