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| Stars that orbit on nearly the same plane |
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| stars whose orbits are inclined at any angle |
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| stars with the smallest abundance of heavy elements |
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| What is the typical hydrogen content of stars that are forming right now in the vicinity of the Sun? |
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| a source of bright radio emission in the center of our galaxy |
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| If you were to take a voyage across the Milky Way, what kind of material would you spend most of your time in? |
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| warm, rarefied clouds of atomic hydrogen |
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| What kinds of objects lie in the halo of our galaxy? |
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| Which kind of star is most likely to be part of the spheroidal population? |
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| We measure the mass of the black hole at the galactic center from: |
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| the orbits of stars in the galactic center. |
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| stars in the central bulge are... |
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| the swirling pattern of stars in the disk surrounded by gas and dust are... |
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| the swirling arms at the edges of the disk contain... |
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| a majority of the bright/blue stars we see as well as the gas and dust |
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| We find more blue stars in the disk and more red stars in the bulge. What do the stars' colors say about their ages? |
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| According to our study of the HR diagram, blue stars have shorter lifetimes than red stars and so they are, on average, younger than red stars. Having a region of the galaxy dominated by young stars means that many new stars need to be forming in the disk, whereas the relatively few stars are forming in the bulge. |
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| how do stars actually form? |
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The first generation of stars (Population III) dispersed heavy elements throughout the galaxy while it was still taking shape
␣ As the gas from these stars expands, it creates bubbles in the interstellar medium (the space between stars), sweeping up material and pushing it outwards |
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| if the gas bubbles are expanding out in all directions, why are their edges so much brighter than their centers? |
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| It is because at the edges we are looking through more material than at the centers; there is more material along the line of sight at the edge than the center |
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| where supernovae most often occur |
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| clouds of cooled hydrogen in the disk that result from absorbed atomic radiation shielding the centers of what were once bubbles of atomic gases |
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| what are the pillars of creation? |
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a region where molecular clouds are incubating stars, offering a form of protection
they have bright edges due to the ionizing radiation of the surrounding stars |
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first objects to form from the protogalactic cloud, outside of the disk and the bulge
since they are out of the disk, they are away from most of the gas and dust, they have essentially been forming in isolation (Madagascar) |
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| if globular clouds are forming in isolation, how would their HR diagram differ from that of the galactic disk? |
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| There would be fewer stars on the upper main sequence, with the most massive stars having died off and no new ones to replace them |
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Older populations will have a main sequence turnoff that is further down the main sequence than younger clusters
they can given us the maximum age of a stellar population
most accurate for globular clusters where the most massive stars are always being replenished and replaced |
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