Question: A star must be hotter than about 25,000 K to produce an H II region. Which of the following stars can produce such regions?
Answer Choices:
G2III
M1Ia
White dwarf
A2V
O9V
B1V
Answer: A2V, O9V, B1V
Question: What is the ISM?
Answer Choices:
Helium gas between stars
The material between stars, concentrated into giant clouds known as nebulae
Fusion in star cores
Explosions of stars
Answer: The material between stars, concentrated into giant clouds known as nebulae
Question: Which of the following is the best candidate to explain cosmic rays?
Answer Choices:
Dust grain accelerated in the Earth’s magnetic field
Particles from the Sun’s solar wind
Galactic or entire galactic supernova explosions
Collisions with vast molecular clouds
Answer: Galactic or entire galactic supernova explosions
Question: What proof do we have of ultra-hot ISM temperatures?
Answer Choices:
X-ray spectra from alcohol molecules
Radio wave absorption in hydrogen gas
Radio wave emissions and spectra of hydrogen atoms with quadruple ionization
X-ray emissions from ISM gas and oxygen atom spectra
Answer: X-ray emissions from ISM gas and oxygen atom spectra
Question: Astronomers estimate that the ISM makes up about ___ of the total mass of the Milky Way Galaxy.
Answer Choices:
42%
15%
5%
75%
Answer: 15%
Question: Which is the most abundant type of hydrogen observed in the universe?
Answer Choices:
H₂
H⁰
All are equally abundant
HII
Answer: H⁰
Question: Elements heavier than hydrogen and helium are found in the ISM. How are they produced?
Answer Choices:
Produced by collisions between atoms in the ISM
Produced inside stars and then ejected into the ISM when the stars die
Hydrogen and helium will bond at low temperatures
Remnants from asteroids and comets
Answer: Produced inside stars and then ejected into the ISM when the stars die
Question: True or False? Most of the ISM is composed of ionized hydrogen (HII).
Answer Choices:
True
False
Answer: False
Question: Radio waves at a wavelength of 21-cm are used to detect…
Answer Choices:
Ultra-hot interstellar gas regions
Complex molecules in molecular clouds
HII regions
HI regions
Answer: HI regions
Question: Suppose a single star has spectral features indicating it has a high surface temperature that emits mostly blue light, but when observed, the star appears red. What is an explanation for this?
Answer Choices:
The star is most likely associated with a hot HII region.
This indicates that the star is moving away rapidly so that the blue light is redshifted by the Doppler effect.
Light from the hot star passes through clouds containing interstellar dust.
The star is much more distant than most stars.
Answer: Light from the hot star passes through clouds containing interstellar dust.
Question: How do astronomers observe cold hydrogen clouds (HI regions) that aren’t near a star?
Answer Choices:
21-cm radiation blocked by Earth’s atmosphere
Use radio telescopes to observe the hydrogen through 21-cm radiation
Use optical telescopes
Use X-ray telescopes
Answer: Use radio telescopes to observe the hydrogen through 21-cm radiation
Question: Which of the following is true concerning HII regions?
Answer Choices:
They are always found near hot stars which cause the surrounding gas to fluoresce.
HII regions are the same as a hydrogen bond orbit layer.
Most of them appear to be greenish in color.
They produce heavy elements as they cool off co-molecular clouds.
Answer: They are always found near hot stars which cause the surrounding gas to fluoresce.
Question: Why do HII regions appear red?
Answer Choices:
Consist of molecular hydrogen gas
Composed of singly ionized hydrogen gas
Composed of completely ionized hydrogen; Balmer hydrogen line emitted
Light from HII regions scatters more interstellar reddening
Answer: Composed of completely ionized hydrogen; Balmer hydrogen line emitted
Question: What would be the source of energy producing hot interstellar regions with temperatures of millions of degrees?
Answer Choices:
Nebular ejection
Free-range nuclear fusion
Supernova explosions
Core implosion of massive stars
Answer: Supernova explosions
Question: The hottest temperatures observed in the ISM are measured in ____ of degrees.
Answer Choices:
Millions
Thousands
Tens
Billions
Answer: Millions