Question 1

If the Hubble parameter is 25 km/s per million light years, how old is the universe?

Accepted Answer

A) 10 × 109 y 
B) 12 × 109 y 
C) 15 × 109 y 
D) 20 × 109 y 
E) 25 × 109 y 
A) 10 × 109 y 
B) 12 × 109 y 
C) 15 × 109 y 
D) 20 × 109 y 
E) 25 × 109 y B

Question 2

What is the parallax angle for Proxima Centauri, which is Earth's nearest star at 4.3 ly?

Accepted Answer

A) 1.2 × 10-14 degrees 
B) 2.1 × 10-4 degrees 
C) 1.2 × 10-7 degrees 
D) 2.1 × 10-7 degrees 
E) 2.1 × 10-14 degrees 
A) 1.2 × 10-14 degrees 
B) 2.1 × 10-4 degrees 
C) 1.2 × 10-7 degrees 
D) 2.1 × 10-7 degrees 
E) 2.1 × 10-14 degrees B

Question 3

A star has absolute luminosity equal to that of the Sun (1.5 × 108 km from the Earth) but is 10 pc away from the Earth. By what factor will it appear dimmer than the Sun?

Accepted Answer

A) 2 × 10-9  
B) 2 × 10-11  
C) 2 × 10-13  
D) 2 × 10-15  
E) 2 × 10-17  
A) 2 × 10-9  
B) 2 × 10-11  
C) 2 × 10-13  
D) 2 × 10-15  
E) 2 × 10-17  C

Question 4

The Earth's orbit has a mean radius of 1.5 × 108 km. Over a six-month period, the apparent position of a particular star varies by 0.00014° due to parallax. How distant is the star, in km?

Accepted Answer

A) 1.2 × 1011 km 
B) 1.2 × 1014 km 
C) 1.2 × 1017 km 
D) 1.2 × 1020 km 
E) 1.2 × 1023 km 
A) 1.2 × 1011 km 
B) 1.2 × 1014 km 
C) 1.2 × 1017 km 
D) 1.2 × 1020 km 
E) 1.2 × 1023 km

Question 5

The Sun has apparent brightness at Earth (1.5 × 108 km away) of B. What would be the apparent brightness of the Sun at Pluto, which is 6.0 × 109 km from the Sun?

Accepted Answer

A) 0.50 B 
B) 0.25 B 
C) 0.063 B 
D) 0.025 B 
E) 0.00063 B 
A) 0.50 B 
B) 0.25 B 
C) 0.063 B 
D) 0.025 B 
E) 0.00063 B

Question 6

It can be shown that the approximate age of the universe is 1/H, where H is the Hubble constant. Taking H = 20 km/s/Mly, estimate the age of the universe, in years.

Accepted Answer

A) 1500 years 
B) 15 thousand years 
C) 15 million years 
D) 15 billion years 
E) 15 trillion years 
A) 1500 years 
B) 15 thousand years 
C) 15 million years 
D) 15 billion years 
E) 15 trillion years

Question 7

Estimate the speed of a galaxy that is 10 billion light-years away.

Accepted Answer

A) 0.1c 
B) 0.3c 
C) 0.5c 
D) 0.7c 
E) 0.9c 
A) 0.1c 
B) 0.3c 
C) 0.5c 
D) 0.7c 
E) 0.9c

Question 8

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

Accepted Answer

A) 0.8 M. 
B) 1.2 M. 
C) 1.4 M. 
D) 1.9 M. 
E) 2.8 M. 
A) 0.8 M. 
B) 1.2 M. 
C) 1.4 M. 
D) 1.9 M. 
E) 2.8 M.

Question 9

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

Accepted Answer

A) 1.4 × 109 ly 
B) 23 Mpc 
C) 76 Mly 
D) 7 Mpc 
E) 1.4 × 107 ly 
A) 1.4 × 109 ly 
B) 23 Mpc 
C) 76 Mly 
D) 7 Mpc 
E) 1.4 × 107 ly

Question 10

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

Accepted Answer

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. 
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.

Question 11

The apparent brightness of a star is 1.0 × 10-12 W/m2 and the peak wavelength is 600 nm. Estimate its distance from us.

Accepted Answer

A) 0.090 pc 
B) 0.90 pc 
C) 9.0 pc 
D) 90 pc 
E) 900 pc 
A) 0.090 pc 
B) 0.90 pc 
C) 9.0 pc 
D) 90 pc 
E) 900 pc

Question 12

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

Accepted Answer

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 
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

Question 13

The Earth's orbit has a mean radius of 1.5 × 108 km. Over a six-month period, the apparent position of a particular star varies by 0.00014° due to parallax. How distant is the star, in ly? (1 ly = 9.46 × 1015 m)

Accepted Answer

A) 0.13 ly 
B) 1.3 ly 
C) 13 ly 
D) 130 ly 
E) 1300 ly 
A) 0.13 ly 
B) 1.3 ly 
C) 13 ly 
D) 130 ly 
E) 1300 ly

Question 14

The cosmic background radiation corresponds to a temperature of about

Accepted Answer

A) 1.4 K. 
B) 2.7 K. 
C) 3.0 K. 
D) 3.3 K. 
E) 3.6 K. 
A) 1.4 K. 
B) 2.7 K. 
C) 3.0 K. 
D) 3.3 K. 
E) 3.6 K.

Question 15

About 1 μs after the Big Bang, the temperature of the universe was about 1013 K. What energy (in eV) does this correspond to?

Accepted Answer

A) 1 neV 
B) 1 keV 
C) 1 MeV 
D) 1 GeV 
E) 1 TeV 
A) 1 neV 
B) 1 keV 
C) 1 MeV 
D) 1 GeV 
E) 1 TeV

Question 16

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

Accepted Answer

A) the same. 
B) twice as much. 
C) half as much. 
D) four times as much. 
E) one-fourth as much. 
A) the same. 
B) twice as much. 
C) half as much. 
D) four times as much. 
E) one-fourth as much.

Question 17

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?

Accepted Answer

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. 
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.

Question 18

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

Accepted Answer

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 
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

Question 19

Black holes

Accepted Answer

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. 
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.

Question 20

If a galaxy is moving away from us at 1.0% of the speed of light, how far away is it from us?

Accepted Answer

A) 14 ly 
B) 140 ly 
C) 140 thousand ly 
D) 140 million ly 
E) 140 billion ly 
A) 14 ly 
B) 140 ly 
C) 140 thousand ly 
D) 140 million ly 
E) 140 billion ly

Exam 44: Astrophysics and Cosmology

If the Hubble parameter is 25 km/s per million light years, how old is the universe?

What is the parallax angle for Proxima Centauri, which is Earth's nearest star at 4.3 ly?

A star has absolute luminosity equal to that of the Sun (1.5 × 108 km from the Earth) but is 10 pc away from the Earth. By what factor will it appear dimmer than the Sun?

The Earth's orbit has a mean radius of 1.5 × 108 km. Over a six-month period, the apparent position of a particular star varies by 0.00014° due to parallax. How distant is the star, in km?

The Sun has apparent brightness at Earth (1.5 × 108 km away) of B. What would be the apparent brightness of the Sun at Pluto, which is 6.0 × 109 km from the Sun?

It can be shown that the approximate age of the universe is 1/H, where H is the Hubble constant. Taking H = 20 km/s/Mly, estimate the age of the universe, in years.

Estimate the speed of a galaxy that is 10 billion light-years away.

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

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

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

The apparent brightness of a star is 1.0 × 10-12 W/m2 and the peak wavelength is 600 nm. Estimate its distance from us.

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

The Earth's orbit has a mean radius of 1.5 × 108 km. Over a six-month period, the apparent position of a particular star varies by 0.00014° due to parallax. How distant is the star, in ly? (1 ly = 9.46 × 1015 m)

The cosmic background radiation corresponds to a temperature of about

About 1 μs after the Big Bang, the temperature of the universe was about 1013 K. What energy (in eV) does this correspond to?

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

If a galaxy is moving away from us at 1.0% of the speed of light, how far away is it from us?

Introduction, Measurement, Estimating

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Special Theory of Relativity

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Nuclear Energy: Efects and Uses of Radiation

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Filters

A star has absolute luminosity equal to that of the Sun (1.5 × 10⁸ km from the Earth) but is 10 pc away from the Earth. By what factor will it appear dimmer than the Sun?

The Earth's orbit has a mean radius of 1.5 × 10⁸ km. Over a six-month period, the apparent position of a particular star varies by 0.00014° due to parallax. How distant is the star, in km?

The Sun has apparent brightness at Earth (1.5 × 10⁸ km away) of B. What would be the apparent brightness of the Sun at Pluto, which is 6.0 × 10⁹ km from the Sun?

The apparent brightness of a star is 1.0 × 10^-¹² W/m² and the peak wavelength is 600 nm. Estimate its distance from us.

The Earth's orbit has a mean radius of 1.5 × 10⁸ km. Over a six-month period, the apparent position of a particular star varies by 0.00014° due to parallax. How distant is the star, in ly? (1 ly = 9.46 × 10¹⁵ m)

About 1 μs after the Big Bang, the temperature of the universe was about 10¹³ K. What energy (in eV) does this correspond to?