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Which part of the galaxy contains the coldest gas? |
The halo |
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Why do disk stars bob up and down as they orbit the galaxy? |
Because the gravity of other disk stars always pulls them toward the disk |
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Which part of the galaxy has gas with the hottest average temperature? |
The halo |
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What is the typical percentage of elements other than hydrogen and helium in stars that are forming in the vicinity of the Sun? |
2% |
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Where would you be most likely to find an ionization nebula? |
In the disk |
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The best measurements of the mass of the black hole at the galactic center come from |
The orbits of stars in the galactic center |
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Where are most of the Milky Way’s globular clusters found? |
In the halo |
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How do we determine the Milky Way’s mass outside of the Sun’s orbit? |
From the orbits of stars and gas clouds orbiting the galactic center at greater distances than the Sun |
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Where would you least expect to find an ionization nebula? |
In the halo |
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What kind of star is most likely to be part of the spheroidal population? |
An M star |
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If we could see our galaxy from 2 million light years away, it would appear |
As a flattened disk with a central buldge and spiral arms |
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How does the interstellar medium affect our view of most of the galaxy? |
It prevents us from seeing most of the galactic disk with visible and ultraviolet light |
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Applying the Newton’s version of Kepler’s third law to the a star orbiting 40,000 light years from the center of the Milky Way galaxy allows us to determine |
The mass of the Milky Way Galaxy that lies within 40,000 light years of the galactic center |
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The most common form of gas in the dism of the Milky Way galaxy is |
Atomic hydrogen gas |
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How should we expect the Milky Way’s interstellar medium to be different in 50 years than it is today? |
The total amount of gas will be much less than it is today |
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Over time, the star- gas- star cycle leads the gas in the Milky Way to |
Have a greater abundance of heavy elements |
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All of the following types of objects are found almost exclusively in the disk(rather than the Halo) of the Milky Way except |
Globular clusters |
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Red and orange stars are found evenly spread throughout the galactic disk, but blue stars are typically found |
Only in or near star forming clouds |
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Spiral arms appear bright because |
They contain more hot young stars than other parts of the disk |
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What is the best evidence for an extremely massive black hole in the center of the Milky Way galaxy? |
The orbits of the stars indicate that the presence of an approximately 4 million solar mass object in a region no larger than our solar system |
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How does the diameter of the disk of the Milky Way compare to its thickness? |
The diameter is 100 times as great as the thickness |
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What do we call the bright, sphere shaped region of stars that occupies the central few thousand light years of the Milky Way Galaxy? |
The galaxy’s buldge |
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The Sun’s location in the Milky Way Galaxy is |
In the galactic disk, roughly halfway between the center and the outer edge of the disk |
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What do we mean when we say interstellar medium? |
The gas and dust that lies in between the stars in the Milky Way galaxy |
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What are Magellanic clouds? |
Two small galaxies that orbit the Milky Way Galaxy |
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How do disk stars orbit the center of the galaxy? |
They all orbit in roughly the same plane and in the same direction |
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Elements heavier than hydrogen and helium constitute about _____ |
2% of the mass of the Milky Way’s interstellar medium |
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What do we mean by the star-gas-star cycle? |
It is the continuous recycling of gas in the galactic disk between stars and the interstellar medium |
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What are cosmic rays? |
Subatomic particles that travel close to the speed of light |
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The primary way that we observe the atomic hydrogen that makes up most of the interstellar gas in the Milky Way is with |
Radio telescopes observing at a wavelength of 21 centimeters |
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Which of the following is the most abundant in molecular clouds |
H2 |
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Interstellar dust consists mostly of |
Microscopic particles of carbon and silicon |
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What do we mean by a protogalactic cloud? |
A cloud of hydrogen and helium that contracts to become a galaxy |
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Most stars in the Milky Way’s halo are |
Very old |
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What is an ionization nebula? |
A colorful cloud of gas that glows because it is heated by light from nearby hot stars |
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Where do most star formation occur in the Milky Way Galaxy? |
In the spiral arms |
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What kind of object do we think lies in the center of the Milky Way galaxy? |
A black hole of about 4 million solar masses |
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