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30 Cards in this Set
- Front
- Back
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Why do we believe that 90 percent of the mass of the Milky Way is in the form of dark matter? |
The orbital speeds of stars far from the galactic center are surprisingly high, suggesting that these stars are feeling gravitational effects from unseen matter in the halo. |
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Where does most star formation occur in the Milky Way today? |
In the spiral arms |
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The Milky Way is tilted on the sky because |
The solar system is tilted compared to the disk of the galaxy. |
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Why was the very first three-dimensional map or our galaxy so incorrect? |
The assumption was made that all stars were the same brightness as our Sun. |
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If you made a plot of open clusters on a star map they would be |
Concentrated along the Galaxy's disk |
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Who first tried to produce a three-dimensional map of our galaxy? |
William Herschel |
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What type of stars are found in the bulge of our galaxy? |
a mix of old and young stars with younger stars concentrated near the center |
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Astronomers believe that the massive object at the center of the Milky Way is a black hole because |
Observations at X-ray infrared and radio limit the size of the object to smaller than 10 AU. |
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What type of stars are found in the disc of our galaxy? |
almost exclusively young; hot stars |
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Where is our Sun located in the galaxy? |
the disc |
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What kinds of objects lie in the visible halo of our Galaxy? |
Globular clusters |
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After determining a supernova is a Type Ia, what other measurement needs to be made so that astronomers can determine the distance to the supernova? |
The apparent magnitude at peak brightness. |
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The ______ theory offers a likely explanation for the formation of _____. |
Density wave; spiral arms |
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The Sun lies _______ the disk of our Milky Way Galaxy. |
About two-thirds of the way out in |
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From the galaxy types listed below, our Milky Way galaxy is best described as a/an |
spiral galaxy. |
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Which of the following is NOT true of population II stars? 1) They make up the arms of spiral galaxies. 2) The make up globular clusters. 3) They make up the central bulge of spiral galaxies. 4) Elliptical galaxies are entirely population II stars. |
1) They make up the arms of spiral galaxies. |
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Rotational velocity outside the visible boundary of our Galaxy is _____ than would be expected on the basis of observed stars and gas; indicating the presence of _____. |
Higher; dark matter |
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Dust and gas in the Milky Way... |
Are concentrated in a thin layer in the disk. |
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How is the mass of our galaxy measured? |
By using a star's period, distance from the center, and using Keplers Third Law |
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In general Population I stars are _________ than Population II stars. |
Younger |
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In what part of the Milky Way are globular clusters? |
the halo |
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According to the density-wave theory spiral arms are blue because they |
Contain a lot of young stars formed from clouds compressed by the density wave. |
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What property of Cepheid variable stars allows one to find the distance to those stars? |
Their luminosity is related to the period between maximum brightness. |
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What is the approximate diameter of the Milky Way Galaxy in light years? |
100000 |
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What type of stars are found in the halo of our galaxy? |
only old; cool stars |
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Most of the stars visible to the naked eye at night are _________ which are _________. This result is a _________. |
Massive luminous stars or evolved giants; some of the least common by number but brightest stars; selection effect |
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The majority of stars in the Milky Way appear to be in the _______. |
Mass range of 0.1 to 0.5 solar masses |
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Stars of globular clusters belong to Population ________. |
II |
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One difference between Population I and Population II stars in the Milky Way is... |
That Pop I stars have orbits in the disk and Pop II stars have orbits that pass through the disk. |
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The coldest star forming regions are associated with |
CO emission lines |
