Question 1

Explain how "forbidden" lines appear in spectra of emission nebulae.

Accepted Answer

These lines correspond to excited states

Question 2

Reflection nebulae usually appear red.

Accepted Answer

A) True 
 B)False

Question 3

Molecular hydrogen can best be detected by ultraviolet observations.

Accepted Answer

A) True 
 B)False

Question 4

In the Milky Way Galaxy, gas and dust are found:

Accepted Answer

A) in molecular clouds. 
B) everywhere. 
C) in neutral hydrogen clouds. 
D) in dark nebulae. 
E) in emission nebulae. 
A) in molecular clouds. 
B) everywhere. 
C) in neutral hydrogen clouds. 
D) in dark nebulae. 
E) in emission nebulae.

Question 5

Interstellar reddening of starlight occurs because the interstellar dust preferentially ________the blue light.

Accepted Answer

The answer of Interstellar reddening of starlight occurs because the...

Question 6

The form of electromagnetic radiation least blocked by a dark nebula is ________.

Accepted Answer

The answer of The form of electromagnetic radiation least blocked...

Question 7

Emission nebulae are blue.

Accepted Answer

A) True 
 B)False

Question 8

The ________ of light passing through thin dust clouds lets us map the Galaxy's magneticfield.

Accepted Answer

A) diffraction 
B) granulation 
C) ionization 
D) polarization 
E) absorption 
A) diffraction 
B) granulation 
C) ionization 
D) polarization 
E) absorption

Question 9

Explain why interstellar molecules are best observed at radio wavelengths.

Accepted Answer

Interstellar molecules are best observed

Question 10

How is 21 cm radiation produced?

Accepted Answer

When the electron orbiting the

Question 11

Astronomers use roman numerals to indicate the ionization state of a gas. Ionized hydrogenis indicated by which of the following symbols?

Accepted Answer

A) H II 
B)  $\mathrm { H } _ { 2 }$ 
C) H I 
D)  $\mathrm { H } _ { 1 } ^ { 1 }$ 
E) H III 
A) H II 
B)  $\mathrm { H } _ { 2 }$ 
C) H I 
D)  $\mathrm { H } _ { 1 } ^ { 1 }$ 
E) H III

Question 12

How does emission of long wavelength radio radiation from neutral hydrogen help usovercome the shortcomings of visible light in mapping out distant parts of our galaxy?

Accepted Answer

It allows us to detect interst

Question 13

Molecular hydrogen is not very useful for mapping molecular clouds because:

Accepted Answer

A) molecular hydrogen does not occur in most molecular clouds. 
B) molecular hydrogen puts out radiation similar to most stars. 
C) molecular hydrogen and atomic hydrogen cannot be distinguished in telescopes. 
D) radiation from carbon monoxide overwhelms radiation from molecular hydrogen. 
E) molecular hydrogen is essentially invisible in the radio portion of the spectrum. 
A) molecular hydrogen does not occur in most molecular clouds. 
B) molecular hydrogen puts out radiation similar to most stars. 
C) molecular hydrogen and atomic hydrogen cannot be distinguished in telescopes. 
D) radiation from carbon monoxide overwhelms radiation from molecular hydrogen. 
E) molecular hydrogen is essentially invisible in the radio portion of the spectrum.

Question 14

What are the very cold (about 20 K), dense clouds of gas thought to be the most massiveobjects in the Galaxy called?

Accepted Answer

A) emission nebulae 
B) absorption clouds 
C) dust clouds 
D) molecular clouds 
E) reflection nebulae 
A) emission nebulae 
B) absorption clouds 
C) dust clouds 
D) molecular clouds 
E) reflection nebulae

Question 15

What feature of interstellar dust is inferred by the polarization of starlight?

Accepted Answer

A) its shape 
B) its composition 
C) its location in space 
D) its presence in molecular clouds 
E) its presence in dark nebulae 
A) its shape 
B) its composition 
C) its location in space 
D) its presence in molecular clouds 
E) its presence in dark nebulae

Question 16

Dust particles and magnetic fields in the interstellar medium are revealed by ________ oflight.

Accepted Answer

The answer of Dust particles and magnetic fields in the...

Question 17

Why can radio waves get through the dust clouds, but light is blocked?

Accepted Answer

The interstellar dust grains a

Question 18

Why does a reflection nebula look blue?

Accepted Answer

The nebula is illuminated by t

Question 19

The temperature inside an H II region is colder than inside an H I region.

Accepted Answer

A) True 
 B)False

Question 20

Neutral hydrogen is most obvious in the electromagnetic spectrum:

Accepted Answer

A) in yellow light of the Sun's continuum. 
B) at 656.3 nm, hydrogen alpha red. 
C) at 21 cm in the radio region. 
D) at 121.3 nm, the Lyman alpha ultraviolet line. 
E) Neutral hydrogen has yet to be detected in space. 
A) in yellow light of the Sun's continuum. 
B) at 656.3 nm, hydrogen alpha red. 
C) at 21 cm in the radio region. 
D) at 121.3 nm, the Lyman alpha ultraviolet line. 
E) Neutral hydrogen has yet to be detected in space.

Exam 18: The Interstellar Medium: Gas and Dust Among the Stars

Explain how "forbidden" lines appear in spectra of emission nebulae.

Reflection nebulae usually appear red.

Molecular hydrogen can best be detected by ultraviolet observations.

In the Milky Way Galaxy, gas and dust are found:

Interstellar reddening of starlight occurs because the interstellar dust preferentially ________the blue light.

The form of electromagnetic radiation least blocked by a dark nebula is ________.

Emission nebulae are blue.

The ________ of light passing through thin dust clouds lets us map the Galaxy's magneticfield.

Explain why interstellar molecules are best observed at radio wavelengths.

How is 21 cm radiation produced?

Astronomers use roman numerals to indicate the ionization state of a gas. Ionized hydrogenis indicated by which of the following symbols?

How does emission of long wavelength radio radiation from neutral hydrogen help usovercome the shortcomings of visible light in mapping out distant parts of our galaxy?

Molecular hydrogen is not very useful for mapping molecular clouds because:

What are the very cold (about 20 K), dense clouds of gas thought to be the most massiveobjects in the Galaxy called?

What feature of interstellar dust is inferred by the polarization of starlight?

Dust particles and magnetic fields in the interstellar medium are revealed by ________ oflight.

Why can radio waves get through the dust clouds, but light is blocked?

Why does a reflection nebula look blue?

The temperature inside an H II region is colder than inside an H I region.

Neutral hydrogen is most obvious in the electromagnetic spectrum:

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 Stars: Giants, Dwarfs, and the Main Sequence

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

Filters