Astronomy – Astronomy Flashcard
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in the disk, 2/3 of the way out from the center
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sun's position in the milky way
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contains Globular clusters spherical in shape, contains pop II stars and very little interstellar gas and dust
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Halo
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-flattened shape -spiral arms -both pop I and pop II stars -interstellar gas, and dust -pop I stars associated with spiral arms
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Galactic disk
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center of the galaxy -football shape -pop II stars -little gas and dust -supermassive blake hole at the center
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Bulge
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a mystery partly because we lack a quantum theory of gravity
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planck epoch
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forces except gravity are unified
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the grand unification epoch
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universe expands rapidly smaller than a proton to bigger than a melon -supported experimentally
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the inflationary epoch
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weak and electromagnetic forces act as one
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electroweak epoch
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what we think of a "normal" elementary particle form and survive
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the quark, hadron and lepton epoch
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atoms form (hydrogen and helium) and cosmic background radiation 'decouples' from matter
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photons, nucleaosythesis and the cosmic background radiation
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atom exist but stars don't
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dark ages
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stars form- quantum fluctuations at the time of inflation determines the distribution of matter in the universe. denser areas are where stars will form -gravity is the major large-scale force
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"modern" era
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a galaxy of Hubble type "e" class with a circular to elliptical outline on the sky containing almost no disk and a population of old stars
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elliptical galaxy properties
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a galaxy of Hubble type "s" class with a discernible disk in which large spiral patterns exist
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spiral/barred spiral galaxy properties
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galaxy without regular or symmetric appearance
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irregular galaxy properties
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over a thousand galaxies
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rich clusters
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contain less than a thousand galaxies -most clusters are poor
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poor clusters
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-the poor cluster that the milky way is apart of -has two large spirals, one small spiral -3 million light years across
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local group
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closest large cluster to us -moderately-rich cluster -contains over 2000 galaxies -10 million light years across
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virgo cluster
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-consists of younger stars, clusters and associations -occur near and in the arms of the milky way and other spiral galaxies -originated from interstellar gas that has undergone various process including supernova explosions -consist of mostly hydrogen and helium but also contain iron, nickel, carbon and other heavier elements
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pop. I
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consists of the oldest stars and clusters -created from interstellar gas clouds that emerged shortly after the big bang -found in the halos of spiral galaxies and in the globular clusters of the milky way
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pop II
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the spiral structure is a wave that moves through the disk causing the stars and gas to clump up along the wave---a density wave. The spiral arms are where the stars pile up as they orbit the center.
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density wave theory
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When a supernova shock wave reaches a gas cloud, it compresses the cloud to stimulate the formation of stars. Some of them will be massive enough to produce their own supernova explosions to keep the cycle going. Coupled with the differential rotation of the disk, the shock waves will keep the spiral arms visible.
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self propagating star formation
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radar ranging
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solar system
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parallax
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nearby stars
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main sequence fitting
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milky way
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cepheids
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nearby galaxies
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distant standards
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galaxy clusters
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hubble's law
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what measures the most distant objects in the universe
