Question 1

In a large sampling of stars, the largest group represented in the H-R diagram will be the mainsequence stars. Why are they so common?

Accepted Answer

Like the Sun, they are young enough to still have most of their initial hydrogen still notfused into helium; they will not evolve off the main sequence until the helium builds up a lot.Since hydrogen is by far the most abundant element and easiest to fuse, most stars are going touse it as their major fuel, as long as this supply lasts. Stars spend the vast majority of their lifespans on the main sequence.

Question 2

In what range of masses are most stars found?

Accepted Answer

A) .1 to 2 solar masses 
B) 1 to 3 solar masses 
C) .1 to 100 solar masses 
D) .01 to 100 solar masses 
E) Stars can have any mass. 
A) .1 to 2 solar masses 
B) 1 to 3 solar masses 
C) .1 to 100 solar masses 
D) .01 to 100 solar masses 
E) Stars can have any mass. C

Question 3

Two stars have apparent magnitudes of 0 and 5. If both stars are 117 parsecs away, which staris intrinsically brighter and by what factor is it brighter than the other?

Accepted Answer

Since both stars are at the same distance (it does not matter what the distance is), themagnitude 0 star is the brightest. It is intrinsically 100 times brighter than the magnitude 5 starbecause 5 magnitudes is always a factor of 100 in intrinsic brightness.

Question 4

Two red stars have surface temperatures of 3000 K, but Star A's luminosity is about 5% ofthe Sun's and Star B's luminosity is about 32,000 times the luminosity of the Sun. How muchbigger is star B than star A?

Accepted Answer

A) They are the same size. 
B) Star B's radius is about 16 times larger than star A's radius. 
C) Star B's radius is about 800 times larger than star A's radius. 
D) Star B's radius is about 640,000 times larger than star A's radius. 
E) This cannot be determined from the information given. 
A) They are the same size. 
B) Star B's radius is about 16 times larger than star A's radius. 
C) Star B's radius is about 800 times larger than star A's radius. 
D) Star B's radius is about 640,000 times larger than star A's radius. 
E) This cannot be determined from the information given.

Question 5

The Hipparcos mission's observations have given us good data on stars out to about:

Accepted Answer

A) 100 light-years. 
B) 200 light-years. 
C) 200 parsecs. 
D) 1000 light-years. 
E) 1000 parsecs. 
A) 100 light-years. 
B) 200 light-years. 
C) 200 parsecs. 
D) 1000 light-years. 
E) 1000 parsecs.

Question 6

Why are spectra of stars different?

Accepted Answer

Spectra of stars differ primarily becaus

Question 7

Having nothing to do with trigonometry, ________ parallaxes use the width of absorptionlines to estimate the star's luminosity and size and distance.

Accepted Answer

A) bolometric 
B) photometric 
C) spectroscopic 
D) holographic 
E) videometric 
A) bolometric 
B) photometric 
C) spectroscopic 
D) holographic 
E) videometric

Question 8

Knowledge of a star's temperature and ________ enables us to calculate its radius, surfacearea, and volume from the appropriate radiation law.

Accepted Answer

luminosity

Question 9

About 500 stars can be seen by the naked eye from somewhere on Earth.

Accepted Answer

A) True 
 B)False

Question 10

The nearest naked-eye star to our Sun, Alpha Centauri, is still over a parsec distant.

Accepted Answer

A) True 
 B)False

Question 11

If a star were moved 10 times farther away, its apparent magnitude would drop by fivemagnitudes.

Accepted Answer

A) True 
 B)False

Question 12

Star A and star B both have an apparent magnitude of 7.0, but star A is at a distance of 15 pcand star B is at a distance of 30 pc. Which statement below is correct?

Accepted Answer

A) Star A appears brighter than star B, but actually star B and star A are the same brightness. 
B) Star B appears brighter than star A, but actually star B and star A are the same brightness. 
C) Star A and star B appear to have the same brightness, but actually star B is brighter than starA. 
D) Star A and star B appear to have the same brightness, but actually star A is brighter than starB. 
E) It is impossible to determine how bright these stars are or appear to be relative to one another,given the information above. 
A) Star A appears brighter than star B, but actually star B and star A are the same brightness. 
B) Star B appears brighter than star A, but actually star B and star A are the same brightness. 
C) Star A and star B appear to have the same brightness, but actually star B is brighter than starA. 
D) Star A and star B appear to have the same brightness, but actually star A is brighter than starB. 
E) It is impossible to determine how bright these stars are or appear to be relative to one another,given the information above.

Question 13

Star A and star B have the same apparent magnitude. Star A is twice as distant as star B.Therefore, star A has twice the luminosity as star B.

Accepted Answer

A) True 
 B)False

Question 14

Star A and star B both have an absolute magnitude of 2.0, but star A is at a distance of 50 pcand star B is at a distance of 20 pc. Which statement below is correct?

Accepted Answer

A) Star A appears brighter than star B, but actually star B and star A are the same brightness. 
B) Star B appears brighter than star A, but actually star B and star A are the same brightness. 
C) Star A and star B appear to have the same brightness, but actually star B is brighter than starA. 
D) Star A and star B appear to have the same brightness, but actually star A is brighter than starB. 
E) It is impossible to determine how bright these stars are or appear to be relative to one another,given the information above. 
A) Star A appears brighter than star B, but actually star B and star A are the same brightness. 
B) Star B appears brighter than star A, but actually star B and star A are the same brightness. 
C) Star A and star B appear to have the same brightness, but actually star B is brighter than starA. 
D) Star A and star B appear to have the same brightness, but actually star A is brighter than starB. 
E) It is impossible to determine how bright these stars are or appear to be relative to one another,given the information above.

Question 15

A type B9 star is hotter than a type A0.

Accepted Answer

A) True 
 B)False

Question 16

What is the typical main sequence lifetime of a G-type star?

Accepted Answer

A) 10 million years 
B) 100 million years 
C) 1 billion years 
D) 10 billion years 
E) 100 billion years 
A) 10 million years 
B) 100 million years 
C) 1 billion years 
D) 10 billion years 
E) 100 billion years

Question 17

What is the absolute magnitude of our Sun?

Accepted Answer

A) -23.0 
B) -4.6 
C) -1.4 
D) +4.8 
E) +9.4 
A) -23.0 
B) -4.6 
C) -1.4 
D) +4.8 
E) +9.4

Question 18

Star A is a main sequence star of spectral type $\mathrm { F 2}$ ad star B is a white dwarf of spectral typeB4. Which statement below is correct?

Accepted Answer

A) Star A appears brighter than star B. 
B) Star B appears brighter than star A. 
C) Star A is hotter than star B. 
D) Star B is hotter than star A. 
E) None of the above can be said about these two stars. 
A) Star A appears brighter than star B. 
B) Star B appears brighter than star A. 
C) Star A is hotter than star B. 
D) Star B is hotter than star A. 
E) None of the above can be said about these two stars.

Question 19

On the H-R diagram, the Sun lies:

Accepted Answer

A) at the top left. 
B) at the bottom left. 
C) at the bottom right. 
D) about the middle of the main sequence. 
E) at the top right. 
A) at the top left. 
B) at the bottom left. 
C) at the bottom right. 
D) about the middle of the main sequence. 
E) at the top right.

Question 20

In a binary system, the more massive stars always stay closer to the center of mass and moveslower.

Accepted Answer

A) True 
 B)False

Exam 17: The Stars: Giants, Dwarfs, and the Main Sequence

In a large sampling of stars, the largest group represented in the H-R diagram will be the mainsequence stars. Why are they so common?

In what range of masses are most stars found?

Two stars have apparent magnitudes of 0 and 5. If both stars are 117 parsecs away, which staris intrinsically brighter and by what factor is it brighter than the other?

Two red stars have surface temperatures of 3000 K, but Star A's luminosity is about 5% ofthe Sun's and Star B's luminosity is about 32,000 times the luminosity of the Sun. How muchbigger is star B than star A?

The Hipparcos mission's observations have given us good data on stars out to about:

Why are spectra of stars different?

Having nothing to do with trigonometry, ________ parallaxes use the width of absorptionlines to estimate the star's luminosity and size and distance.

Knowledge of a star's temperature and ________ enables us to calculate its radius, surfacearea, and volume from the appropriate radiation law.

About 500 stars can be seen by the naked eye from somewhere on Earth.

The nearest naked-eye star to our Sun, Alpha Centauri, is still over a parsec distant.

If a star were moved 10 times farther away, its apparent magnitude would drop by fivemagnitudes.

Star A and star B both have an apparent magnitude of 7.0, but star A is at a distance of 15 pcand star B is at a distance of 30 pc. Which statement below is correct?

Star A and star B have the same apparent magnitude. Star A is twice as distant as star B.Therefore, star A has twice the luminosity as star B.

Star A and star B both have an absolute magnitude of 2.0, but star A is at a distance of 50 pcand star B is at a distance of 20 pc. Which statement below is correct?

A type B9 star is hotter than a type A0.

What is the typical main sequence lifetime of a G-type star?

What is the absolute magnitude of our Sun?

Star A is a main sequence star of spectral type F2\mathrm { F 2}F2 ad star B is a white dwarf of spectral typeB4. Which statement below is correct?

On the H-R diagram, the Sun lies:

In a binary system, the more massive stars always stay closer to the center of mass and moveslower.

Charting the Heavens: The Foundations of Astronomy

The Copernican Revolution: The Birth of Modern Science

Radiation: Information From the Cosmos

Spectroscopy: the Inner Workings of Atoms

Telescopes: The Tools of Astronomy

The Solar System: Comparative Planetology and Formation Models

Earth: Our Home in Space

The Moon and Mercury: Scorched and Battered Worlds

Venus: Earths Sister Planet

Mars: a Near Miss for Life

Jupiter: Giant of the Solar System

Saturn: Spectacular Rings and Mysterious Moons

Uranus and Neptune: The Outer Worlds of the Solar System

Solar System Debris: Keys to Our Origin

Exoplanets: Planetary Systems Beyond Our Own

The Sun: Our Parent Star

The Interstellar Medium: Gas and Dust Among the Stars

Star Formation: a Traumatic Birth

Stellar Evolution: The Life and Death of a Star

Stellar Explosions: Novae, Supernovae, and the Formation of the Elements

Neutron Stars and Black Holes: Strange States of Matter

The Milky Way Galaxy: a Spiral in Space

Galaxies: Building Blocks of the Universe

Galaxies and Dark Matter: The Large-Scale Structure of the Cosmos

Cosmology: The Big Bang and the Fate of the Universe

The Early Universe: Toward the Beginning of Time

Life in the Universe: Are We Alone

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Star A is a main sequence star of spectral type $\mathrm { F 2}$ ad star B is a white dwarf of spectral typeB4. Which statement below is correct?