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Definitions |
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Helium Burning (HB)
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helium "ash" fuses to carbon, some oxygen at core, shell is still fusing hydrogen -> helium
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Globular Star Clusters
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-have up to 1 million stars
-up to 300 light years
-large mass of cluster allows gravity to hold the cluster together
-stars in this cluster can be old or young
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Protostar 3
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core warming due to gravitational contraction, heat builds up.
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Oldest white dwarfs are about...
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12.7 billion years old
-cooling rate
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Owl Nebula...
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-planetary nebula (carbon "ash" core becomes a white dwarf star and the outer layers of the star are gently ejected, forming a nebula)
-near the end of its life
-within the Owl Nebula are four stars with the brighter white dwarf at the center
-in the background are several smaller fuzzy objects that are most likely distant galaxies.
-4x300s
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Evidence that black holes exist
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-stars/other things orbit it
-light around it gets distorted
-stuff falling into it emits light
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Pulsars
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-discovered in 1967
-a rotating neutron star that beams radiation along its magnetic axis.
-searchlight effect
-spins fast, up to 1,000 times a second
-emits light from magnetic poles
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How do we find the age of star clusters?
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find the turnoff point on the H-R diagram where one star diverges from the main sequence.
-where the one star falls on the H-R diagram can represent where the majority of the other stars will fall, therefore representing the age of the cluster.
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What elements are found in high-mass stars?
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-helium through iron
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Main Sequence
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hydrogen and helium core
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High-Mass stars end their lives as...
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neutron stars or black holes.
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Low-Mass stars end their lives as...
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white dwarves.
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Red Giant (again)
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carbon/oxygen in core, shell around core is fusing helium -> carbon, shell around that is fusing hydrogen -> helium
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What elements are found in the Big Bang?
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-hydrogen
-helium
-lithium
-beryllium
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Observed Parameters:
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Matter: critical density = 0.269+/-0.007
Dark Energy: 0.726+/-0.015
Age: 13.72+/-0.12 billion years
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Neutron Star
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-created by collapse of the supernova's iron core
-mass=1.4-3 solar masses
-radius=15-30 km
-composed entirely of neutrons
-hydrostatic equilibrium applies through neutrons being packed together so much that it is impossible for them to flatten.
-extremely dense, one teaspoon of this would be greater than the mass of a mountain
-no protons or electrons
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Black Hole
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a very large mass in small space where gravity is very strong.
-no type of pressure can maintain hydrostatic equilibrium with such a large force.
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Universe is...
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13.7+/-0.2 billion years old
-expansion rate
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In what order do scientists place these events?
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-time begins
-CMBR emitted
-first stars
-solar system forms
-now
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Schwarzschild Radius
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-also called "event horizon"
-to get past it, matter must move faster than the speed of light (300,000 km/s)
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Star Cluster
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group of stars that form out of the same interstellar gas cloud at the same time. All stars in the cluster are about the same age and start on the main sequence at about the same time.
-the cluster produces more low-mass stars than high-mass stars because one big star would be ripped apart by gravity.
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White Dwarf
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-mass similar to sun with a radius similar to the earth.
-extremely dense
-composed of carbon or carbon + oxygen
-hydrostatic equilibrium applies through degenerate electron pressure (electrons are touching instead of repelling one another)
-calculate age by finding mass and temperature through composition and determining the cooling rate by using the current temperature to figure out the time since the white dwarf started
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Fusion of Heavy Elements
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-crush of gravity in high-mass stars keeps its carbon core so hot that degenerate electron pressure never comes into play.
-sequence of fusion stages occur through successive helium-capture reactions
-carbon -> oxygen -> neon -> sodium -> silicon -> iron
-leaves an iron core, the only element that can not generate any tope of nuclear energy.
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Oldest moon rocks and meteorites show that the solar system is...
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4.6 million years old
-radioactive dating
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What elements are found in low-mass stars?
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-helium
-carbon
-oxygen
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Protostar 2
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collapsing cloud of gas and dust.
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What elements are found in supernova shockfronts?
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-iron and anything more massive than iron
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Oldest star clusters are about...
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12 billion years old
-star life cycle
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Collapse
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-takes only 1/4 of a second
-the iron core's nuclei are broken apart by extreme heat (light).
-forces electrons into protons to make neutrons.
-goes from the size of the earth to an approximate 20 km neutron star/black hole
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The most distant galaxies are at least...
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9 billion years old
-light travel time
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Supernova Explosion
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-iron core of red giant collapses (core = white dwarf)
-neutron rich core rebounds (core = neutron star)
-the shock waves move outward through the star
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Red Giant
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helium "ash" used up, hydrogen used up, shell produced around core (helium -> hydrogen)
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Open Star Cluster
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-has a few hundred stars
-smaller than 30 light years
-not enough mass for gravity to hold the cluster together permanently, therefore stars in the cluster are young (blue)
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