Question 1

Why doesn't warm, dense hydrogen emit 21-cm radiation?

Accepted Answer

The 21-cm radiation is another example o

Question 2

What are "forbidden lines"? Briefly describe how they form.

Accepted Answer

Forbidden lines are certain lines in the

Question 3

List the three types of nebulae in the Interstellar Medium.

Accepted Answer

H II  regions (or em

Question 4

Because blue light has a shorter wavelength than red light, it will be more readily scattered.

Accepted Answer

A) True 
 B)False

Question 5

The type of radiation that is emitted when the electron in a hydrogen atom experiences a spin flip is a (n) _______________.

Accepted Answer

The answer of The type of radiation that is emitted...

Question 6

The emission lines from O III are called ____ because they are not visible laboratories on Earth due to the much greater pressure of the gas on Earth.

Accepted Answer

A)  unique lines 
B)  unresolved lines 
C)  forbidden lines 
D)  unseen lines 
E)  "fathom" lines 
A)  unique lines 
B)  unresolved lines 
C)  forbidden lines 
D)  unseen lines 
E)  "fathom" lines

Question 7

Interstellar extinction and the reddening of light by the interstellar medium (ISM) are both caused by _____.

Accepted Answer

A)  atoms and molecules in the ISM 
B)  only  atoms in the ISM 
C)  only molecules in the ISM 
D)  only dust in the ISM 
E)  dust, atoms and molecules of the ISM 
A)  atoms and molecules in the ISM 
B)  only  atoms in the ISM 
C)  only molecules in the ISM 
D)  only dust in the ISM 
E)  dust, atoms and molecules of the ISM

Question 8

Stars are born in reflection nebulae.

Accepted Answer

A) True 
 B)False

Question 9

Coronal gas emits x-rays and has temperatures of ____.

Accepted Answer

A)  $10 ^ { 6 }$ K o r higher 
B)  more than $10 ^ { 4 }$ K but less than $10 ^ { 6 }$ K 
C)  5000 K 
D)  between1000 K to 5000 K 
E)  less than 500K 
A)  $10 ^ { 6 }$ K o r higher 
B)  more than $10 ^ { 4 }$ K but less than $10 ^ { 6 }$ K 
C)  5000 K 
D)  between1000 K to 5000 K 
E)  less than 500K

Question 10

Why is the sky blue during the day?

Accepted Answer

The sky appears blue during th

Question 11

Describe three ways in which astronomers can distinguish between interstellar absorption lines and stellar absorption lines.

Accepted Answer

Some stellar spectra contain absorption

Question 12

What observations indicate the presence of dust in the interstellar medium?

Accepted Answer

The dust in the ISM makes distant stars

Question 13

Stars are born from the interstellar medium, and aging or dying stars return gas and dust back into the interstellar medium.

Accepted Answer

A) True 
 B)False

Question 14

Large molecular clouds will form into protostars because of ____.

Accepted Answer

A)  the thermal motions of the atoms in the gas cloud 
B)  gravitational contraction 
C)  radiation pressure from nearby stars 
D)  the temperature reaching a critical point 
E)  condensation of dust and gas 
A)  the thermal motions of the atoms in the gas cloud 
B)  gravitational contraction 
C)  radiation pressure from nearby stars 
D)  the temperature reaching a critical point 
E)  condensation of dust and gas

Question 15

_______________ require that a young hot star (T ≥ 25,000 K) be relatively nearby.

Accepted Answer

The answer of _______________ require that a young hot star...

Question 16

The interstellar medium is composed of mainly _____.

Accepted Answer

A)  equal parts of gas and dust 
B)  mostly dust and some gas 
C)  mostly gas and some dust 
D)  dust only 
E)  gas only 
A)  equal parts of gas and dust 
B)  mostly dust and some gas 
C)  mostly gas and some dust 
D)  dust only 
E)  gas only

Question 17

Molecular clouds are mapped using _____ gas instead of the most-abundant hydrogen because itradiates at radio wavelengths more efficiently.

Accepted Answer

A)  oxygen III 
B)  oxygen II 
C)  helium II 
D)  carbon monoxide 
E)  carbon dioxide 
A)  oxygen III 
B)  oxygen II 
C)  helium II 
D)  carbon monoxide 
E)  carbon dioxide

Question 18

Which type of nebula is produced when a star, hotter than 25,000 K, excites the gas near it to produce an emission spectrum producing a distinctive pink color?

Accepted Answer

A)  emission nebulae 
B)  H I 
C)  reflection nebulae 
D)  dark nebulae 
E)  spectral type B6 
A)  emission nebulae 
B)  H I 
C)  reflection nebulae 
D)  dark nebulae 
E)  spectral type B6

Question 19

Calculations of the Sun's future evolution indicate that it will blow away almost half of its mass in several relatively short episodes about 4 to 5 billion years from now before it is finally extinguished.

Accepted Answer

A) True 
 B)False

Question 20

Elements such as carbon, silicon and oxygen have been produced in stars and expelled as stars age in the interstellar medium. This is most likely due to these elements having cooled and condensed from aging stars to form dust grains, and carried out by a powerful winds.

Accepted Answer

A) True 
 B)False

Exam 10: The Interstellar Medium

Why doesn't warm, dense hydrogen emit 21-cm radiation?

What are "forbidden lines"? Briefly describe how they form.

List the three types of nebulae in the Interstellar Medium.

Because blue light has a shorter wavelength than red light, it will be more readily scattered.

The type of radiation that is emitted when the electron in a hydrogen atom experiences a spin flip is a (n) _______________.

The emission lines from O III are called ____ because they are not visible laboratories on Earth due to the much greater pressure of the gas on Earth.

Interstellar extinction and the reddening of light by the interstellar medium (ISM) are both caused by _____.

Stars are born in reflection nebulae.

Coronal gas emits x-rays and has temperatures of ____.

Why is the sky blue during the day?

Describe three ways in which astronomers can distinguish between interstellar absorption lines and stellar absorption lines.

What observations indicate the presence of dust in the interstellar medium?

Stars are born from the interstellar medium, and aging or dying stars return gas and dust back into the interstellar medium.

Large molecular clouds will form into protostars because of ____.

_______________ require that a young hot star (T ≥ 25,000 K) be relatively nearby.

The interstellar medium is composed of mainly _____.

Molecular clouds are mapped using _____ gas instead of the most-abundant hydrogen because itradiates at radio wavelengths more efficiently.

Which type of nebula is produced when a star, hotter than 25,000 K, excites the gas near it to produce an emission spectrum producing a distinctive pink color?

Calculations of the Sun's future evolution indicate that it will blow away almost half of its mass in several relatively short episodes about 4 to 5 billion years from now before it is finally extinguished.

Elements such as carbon, silicon and oxygen have been produced in stars and expelled as stars age in the interstellar medium. This is most likely due to these elements having cooled and condensed from aging stars to form dust grains, and carried out by a powerful winds.

Here and Now

A Users Guide to the Sky

Moon Phases and Eclipses

Origins of Modern Astronomy

Gravity

Light and Telescopes

Atoms and Spectra

The Sun

The Family of Stars

Formation and Structure of Stars

Stellar Evolution

Deaths of Stars

Neutron Stars and Black Holes

The Milky Way Galaxy

Galaxies

Supermassive Black Holes and Active Galaxies

Modern Cosmology

Origin of the Solar System and Extrasolar Planets

Earth the Active Planet

The Moon and Mercury

Venus and Mars

Jupiter and Saturn

Uranus Neptune Pluto and the Kuiper Belt

Meteorites Asteroids and Comets

Astrobiology

Filters