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15 Cards in this Set
- Front
- Back
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Cepheid Variables
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Star whose luminosity varies in characteristic way, with a rapid rise in brightness followed by a slower decline. The period of a Cepheid variable star is related to its luminosity so a determination of this period can be used to obtain an estimated of the star's distance
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galactic disk
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am immense, circular, flattened region containing most of our Galaxy's luminous stars and interstellar matter
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Galactic halo
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Region of a galaxy expanding fa above and below the galactic disk, where globular clusters and other old stars reside
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Galaxy
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Gravitationally bound collection of a large number of stars. the Sun is a star in the Milky Way Galaxy
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Gravitational Lensing
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effect induced on the image of a distant object by a massive foreground object. Light from the distant object is bent into two or more separate image
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Milky Way Galaxy
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spiral galaxy in which the sun resides. the disk of our galaxy is visible in the night sky as the faint band of light known as the milky way
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Period Luminosity relationship
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a relation between the pulsation period of a Cepheid variable and its absolute brightness. Measurement of the pulsation period allows the distance of the star to be determined
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Rotation Curve
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Plot of the orbital speed of disk material in a galaxy against its distance from the galactic center. Analysis of rotation curves of spiral galaxies indicates the existence of dark matter
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RR Lyrae variables
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Variable star whose luminosity changes in a characteristic way. All RR Lyrae stares have more or less the same average luminosity
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Self-propagating star formation
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mode of star formation in which shock waves produced y the formation and evolution of one generation of stars triggers the formation of the next
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Spiral Arms
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distribution of material in a galaxy forming a pinwheel-shaped design, beginning near the galactic center
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Spiral Density waves
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a wave of matter formed in the plane of planetary rings, similar to ripples on the surface of a pond, which wrap around the rings forming spiral patterns similar to grooves in a record disk. Spiral density waves can lead to the appearance of ringlets
a proposed explanation for the existence of galactic spiral arms, in which coiled waves of gas compression through the galactic disk, triggering star formation |
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Variable stars
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a star whose luminosity changes with time
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dark matter
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term used to describe the mass in galaxies and cluster whose existence we infer from rotation curves and other techniques but that has not been confirmed by observations a any electromagnetic wavelength
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Dark Halo
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Region of a galaxy beyond the visible halo where dark matter id believed to reside
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