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22 Cards in this Set
- Front
- Back
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What did Newton measure in the 17th century ?
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The distance to a star called Sirius
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How did Newton measure the distance to Sirius?
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By comparing its luminosity to that of Saturn
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What factor did Newton fail to take into account when he made his estimate ?
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That Saturn is a planet so it does not produce light
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What is parallax ?
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Parallax is an apparent shift in position of a nearby object when it is viewed from two different points
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When do astronomers take measure of parallax ? Why ?
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Every six months
Because that is how long it takes the earth to move from one end of the orbital base line to the other |
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Why can't we use parallax and triangulation to measure the distance to far-away stars?
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Because the farther away an object is, the less parallax there is, making it harder to detect any shift and also harder to detect the angles for triangulation
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What are cepheid variables ?
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Stars that's pulsate in size and brightness at a predictable rate
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Cepheid Variables can be used to measure distances to far-away stars. How do astronomers use the predictable rate of the pulsate ( size and brightness ) of a star ?
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By analyzing other variable stars and the realities distances
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What are two important measurements that Cepheid Variables have allowed ?
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The size of the Milky Way and the distance between other galaxies
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What I the Milky Way ?
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400 billion stars that completely circles the earth
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What is a galaxy ?
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A huge group of stars, gas, and dust held together by gravity
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What is a cluster ?
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A collection of stars
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What is an open cluster ?what is
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An open cluster contains 50-1000 stars that lie along the band of the Milky Way
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What is a globular cluster ?
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A globular cluster 100 000-1 000 000 stars stars grouped together in a spherical shape lies along the southern region of the sky
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How is the Milky Way shaped
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Like a disk
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The Milky Way is ____________ light years in diameter
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75 000
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The is earth located in the Milky Way
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25 000 light years from the central region
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Where are the open clusters in the Milky Way ?
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Outside the central region
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Where are the globular clusters in the Milky Way ?
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Surrounding the center
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What discovery did Edwin Hubble make about the nebula ?i
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He could spot the individual stars
He spotted another galaxy |
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It is estimated that there are about _____________ other galaxies in the universe
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Hundreds
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What are 3 types of galaxies
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1. Elliptical Galaxy
2. Spiral galaxy 3. Irregular galaxy |
