Question 1

H II emission nebula regions are found around _____________.

Accepted Answer

high temperature stars,giant molecular cloud

Question 2

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

Accepted Answer

A)   106 K  o r  higher
B)   more than 104  K but less than 106 K
C)   5000 K
D)   between 1000 K to 5000 K
E)   less than 500 K A

Question 3

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

Accepted Answer

The 21-cm radiation is another example of a forbidden line, which is an emission line from cold, neutral hydrogen gas in the interstellar medium. A hydrogen atom consists of one proton and one electron.  The ground state has two energy levels, leaving two ways for the electron to spin.  If the electron is spinning one way, it can flip over and spin the other way, releasing excess energy as a photon with a wavelength of 21 cm. 
That transition is statistically very unlikely, and it isn't detected in laboratories on Earth because the gas is too dense and warm, and the atoms collide too often.  In space, however, hydrogen atoms collide only rarely, and hydrogen atoms can go undisturbed for millions of years, allowing them to produce the 21-cm emission line.

Question 4

The interstellar reddening does not shift the _______________ of spectral lines, as does the Doppler effect.

Accepted Answer

The answer of The interstellar reddening does not shift the...

Question 5

The _______________ is a high temperature, low density region in the interstellar medium around the Sun.

Accepted Answer

The answer of The _______________ is a high temperature, low...

Question 6

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

Accepted Answer

The answer of Describe three ways in which astronomers can...

Question 7

Briefly discuss the gas-stars-gas cycle.

Accepted Answer

The answer of Briefly discuss the gas-stars-gas cycle....

Question 8

The ground state of hydrogen has two closely-spaced energy levels, where one-electron is spinning up and the other is spinning down. This energy transition corresponds to releasing excess energy as a photon at what wavelength?

Accepted Answer

A)   21 centimeters
B)   21 millimeters
C)   21 meters
D)   22.2 centimeters
E)   22.2 millimeters

Question 9

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

Accepted Answer

A) True 
 B)False

Question 10

Coronal gas radiates energy at ______________ wavelengths.

Accepted Answer

The answer of Coronal gas radiates energy at ______________ wavelengths....

Question 11

_______________ is believed to be produced by supernova explosions.

Accepted Answer

The answer of _______________ is believed to be produced by...

Question 12

The coronal gas in the interstellar medium has very high temperatures similar to the Sun's corona.

Accepted Answer

A) True 
 B)False

Question 13

Match between columns Premises: The part of the ISM that can only be detected with X-ray telescopes have has temperatures of 10 ⁶ K or higher The coolest temperature ISM clouds of cool gas of only about 100 K and dust with densities ranging up to 100 atoms per cubic centimeter and observed only at infrared and radio wavelengths The hot space of ISMs with temperatures of a few thousand K and a density of only 0.1 atom per cubic centimeter found between the cool H I clouds Clouds of gas and dust with densities ranging from 100s to 1000s particles per cubic centimeter, found deep inside the ISM, where it is protected from UV photons Highly ionized state A chaotic shape that is usually twisted, flattened, and tangled

Accepted Answer

The Answer of H I cloud and Molecular clouds and is...

Question 14

What is the most abundant element in the interstellar medium?

Accepted Answer

A)   carbon
B)   iron dust
C)   carbon dust
D)   helium
E)   hydrogen

Question 15

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

Question 16

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

Accepted Answer

The answer of What are "forbidden lines"? Briefly describe how...

Question 17

Which molecule has not been detected in molecular clouds?

Accepted Answer

A)   ethyl alcohol
B)   nitrous oxide
C)   molecular hydrogen
D)   carbon monoxide
E)   All of these have been detected.

Question 18

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

Question 19

Molecules in the interstellar medium emit radiation at what wavelengths?

Accepted Answer

A)   radio
B)   microwave
C)   visible light
D)   ultraviolet
E)   X-ray

Question 20

Stars are born in reflection nebulae.

Accepted Answer

A) True 
 B)False

Exam 10: The Interstellar Medium

H II emission nebula regions are found around _____________.

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

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

The interstellar reddening does not shift the _______________ of spectral lines, as does the Doppler effect.

The _______________ is a high temperature, low density region in the interstellar medium around the Sun.

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

Briefly discuss the gas-stars-gas cycle.

The ground state of hydrogen has two closely-spaced energy levels, where one-electron is spinning up and the other is spinning down. This energy transition corresponds to releasing excess energy as a photon at what wavelength?

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

Coronal gas radiates energy at ______________ wavelengths.

_______________ is believed to be produced by supernova explosions.

The coronal gas in the interstellar medium has very high temperatures similar to the Sun's corona.

Match the four components of the interstellar medium (ISM) with their respective description. You may use the choices more than once.

What is the most abundant element in the interstellar medium?

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?

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

Which molecule has not been detected in molecular clouds?

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.

Molecules in the interstellar medium emit radiation at what wavelengths?

Stars are born in reflection nebulae.