Astronomy Final Chapter 13 Quiz HSU – Flashcards
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What useful purpose did RR Lyrae stars serve for Harlow Shapley in locating the galactic center?
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Their brightness variations allowed accurate distances to be measured.
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What is the name given to a galaxy with a large nuclear bulge and tightly wound arms starting from a bar through the nuclear bulge?
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SBa.
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Where is the Sun located in our galaxy?
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In or close to the Orion arm, which is between the Sagittarius and Perseus arms.
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Who developed the classification system that divides galaxies into spiral, elliptical, and irregular and classifies spirals by the size of their nuclear region and the tightness of winding of their arms?
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Edwin Hubble
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What name is given to a galaxy with a smooth distribution of brightness and a round shape?
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E0
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What is the Local Group?
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A cluster of about 30 galaxies of which the Milky Way is a member.
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Which two parameters of star motion in a galaxy are represented by its rotation curve?
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Orbital speed as a function of star distance from the galactic center.
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An astronomer studying a distant cluster of galaxies finds that several of the galaxies are spiral-shaped, with a large nuclear region and tightly wound arms. How should the astronomer classify these galaxies?
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Sa
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Harlow Shapley first located the center of our Galaxy in 1917 by
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observing the distribution of globular clusters in the galactic halo.
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The Magellanic Clouds seen from the southern hemisphere are examples of what type of objects?
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Irregular galaxies
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A particular galaxy has a nuclear region of more or less uniform brightness from which long lanes of stars curve outward. What type of galaxy is this?
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Spiral
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What is a barred spiral galaxy?
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A spiral galaxy with a straight bar instead of a nuclear bulge.
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When distances were carefully measured from Earth to globular clusters above and below the Milky Way plane (where our view of them is not obscured by interstellar dust and gas), their distribution was found to be
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spherically symmetric about a point in the constellation Sagittarius and concentrated in that direction.
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What is the galactic halo?
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A spherical distribution of stars and globular clusters centered on the nuclear bulge.
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Who first discovered that the majority of galaxies are moving away from the Earth?
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Edwin Hubble
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What method is used to determine the distances of very remote galaxies?
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Use of their spectral redshifts and the Hubble law
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What name is given to a galaxy with a smooth distribution of brightness and a very elongated shape?
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E7.
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The factor that misled Herschel into concluding that the stars of the Milky Way were distributed with the Sun at the center of the Galaxy was
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interstellar dust, which obscured the more distant stars and thereby localized his observations.
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An astronomer studying a distant cluster of galaxies finds that several of the galaxies are spiral-shaped, with a nuclear region of moderate size and moderately wound arms. How should the astronomer classify these galaxies?
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Sb.
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The Hubble law, representing observations of distant objects in the universe, relates which two parameters
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The distance to a distant object and the redshift of its light.
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What is the Hubble classification for a spiral galaxy with a small nuclear region and loosely wound arms?
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Sc
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The Milky Way Galaxy appears to have a spiral structure with
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four separate major arms.
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The primary evidence for the expanding universe concept is
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the redshift of light from distant galaxies, which increases with distance of the galaxy from Earth.
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In the 1780's, Sir William Herschel tried to measure the Sun's position in our Galaxy by
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counting the density of stars in different directions along the Milky Way
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The dimensions of the disk of our Milky Way Galaxy are
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diameter 100,000 light-years; thickness 2,000 light-years.
