Astronomy Exam 3 Answers – Flashcards
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Spiral Galaxies
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(denoted by S, and class a,b,or c) contain a flattend galactic disk, dense nucleous, wide variety of shapes.
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Barred- Sprial galaxy
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Has presence of an elongated "bar" of stellar and interstellar matter.
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elliptical galaxies
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no spiral arms and no obvious galactic disk, little internal structure.
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Standard Candles
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easily recognizable candles, usuually aplies to very bright objects
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Tully-Fisher relation
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used to obtain accurate estimate of a spiral galaxy's luminosity by observing how fast it rotates
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Galaxy Cluster
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a collection of galaxiesheld together by their mutal gravitation
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Hubble's Constant
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Recessional Velocity = H0 x distance Constant of proportionality between the velocities of remote galaxies and their distances. The slope of the line on the hubble diagram
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Seyfert galaxies
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Class of astronomical objects whose properties lie between those of normal galaxies and those of the most energetic galaxies known.
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Radio Galaxies
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active galaxies, emit large amounts of energy in the radio portion of the electromagnetic spectrum.
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Quasars
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Are not stars but, enormously bright, distant galaxy with a giant black hole at its center.(have been observed in all partsof the electromagnetic spectrum)
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Properties of Active Galatic Nuclei
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Hight luminosities, Mostly nonstellar, variable, Jets/other explosive activity, rapid internal motion, & interactions between galaxies.
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Synchrotron radiation
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the radiation emitted by charged particles moving through a magnetic field; nonthermal radiation (no link between emission and the temperature of the radiated object.)
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S0&SB0 Galaxies
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intermediate, in their properties between elliptical and spirals.
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Irregular galaxies
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Do not fit into any of the other categories. Many are rich in gas and dust and are the sites of vigorous star formation.
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Galactic Bulge
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Thick distribution of warm gas and the stars around the center of a galaxy.
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Galactic disk
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flattend region of gas and dust, this is the region of active star formation.
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Variable stars
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stars that alternately grow brighter and dimmer as their outer layers expand and contract in size(can be used to study halos)
