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24 Cards in this Set
- Front
- Back
A cluster of stars, gases, and dust held together by gravity is called a(n)______.
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galaxy
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What is the universe?
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All of space and everything in it.
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Most of the universe is _________.
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empty space
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Why don't scientists measure distances to stare in Kilometers?
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Distances to stars are so large that the Kilometer is not a very practical unit.
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What is a light-year?
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The distance that light travels in one year, or about 9.5 million million Kilometers.
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True or false?
THe light-year is a unit of time. |
false
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What is parallax?
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The apparent change in position of an object when you look at it from different positions.
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Which one of these is what astronomers use parallax to measure the distance to.
a)distant stars b)the Sun c)the planets d)nearby stars |
d)nearby stars
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To measure parallax shift,astronomers look at the same star twice, when Earth is on different sides of the ____.
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Sun
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What are the three main characteristics used to describe stars?
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a.size
b. temperature c.brightness |
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Stars that are much larger than the Sun are called ______.
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giant stars or supergiant stars
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WHich kinds of stars are smaller than the sun?
a. neutron star b. giant star c. supergiant star d. white dwarf star |
a. neutron star
d. white dwarf star |
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What reveals a star's temperature?
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Its color
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What is revealed by the red color of the supergiant star called Betelgeuse?
a. it is an extremely hot star b. it is in a constellation c. it is far away d. it is a cool star |
d. it is a cool star
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THe amount of light a star gives off is called its _________.
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brightness
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WHy does Rigel shine as brightly as Betelgeuse, even though Rigel is much smaller than Betelgeuse?
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Rigel is very hot, so it gives off a lot of light.
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How bright a star looks from Earth depends on what two factors?
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a. How far the star is from Earth
b. How bright the star actually is |
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What are the 2 measurements of brightness and their definitions?
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a. Apparent magnitude- a star's brightness as seen from Earth
b. Absolute magnitude- the brightness a star would have if it were a standard distance from Earth |
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True or false? THe closer a star is to Earth, the brighter it is.
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false
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What two things must an astronomer find out in order to calculate a star's absolute magnitude?
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a. the star's apparent magnitude
b. the star's distance from Earth |
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THe diagram that shows the relationship between the surface temperature and the brightness of stars is called the _________.
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Hertzsprung- Russel Diagram
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WHat is measured on the x- and y- axes of the H-R Diagram?
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x-axis- surface temperature (C)
y-axis- brightness |
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An area on the H-R Diagram that runs from the upper left to the lower right and includes more than 90 percent of stars is called the ___________.
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main sequence
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Which of these is true based on the H-R diagram?
a. THe sun is a main- sequence star b. white dwarfs are brighter than supergiants c. Rigel is hotter than Betelgeuse d.Polaris is brighter than the Sun |
a, c, d
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