Alex Filippenko
1) Understanding the Universe: An Introduction to Astronomy, 2nd Edition: The Corpses of Massive Stars
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The imploding core of a Type II supernova typically forms a bizarre, enormously compact object called a neutron star, consisting entirely of tightly packed neutrons, a teaspoon of which would weigh about a billion tons.
12) Understanding the Universe: An Introduction to Astronomy, 2nd Edition: The Quest for Black Holes
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Because they don't emit any light, black holes can't be seen directly. But they reveal their presence through their gravitational influence on other objects. This lecture looks at the methods astronomers use to track them down.
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Why is the sky dark at night? In an infinitely old and large Universe the sky should be ablaze with light at all times. There are several possible answers to this paradox, each of which has profound cosmological implications. The relative youth of the Universe is now known to be the main explanation.
16) Understanding the Universe: An Introduction to Astronomy, 2nd Edition: The Diverse Sizes of Stars
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This lecture discusses the Hertzsprung-Russell diagram, a plot of stellar surface temperature versus luminosity that contains a wealth of information. Stars spend most of their existence on the diagram's well-defined main sequence; outliers include supergiants and white dwarfs.
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According to general relativity, the fate of the Universe is tied to its global geometry. If the Universe has positive curvature, like a sphere, it must eventually collapse in a "Big Crunch." If it is flat or has negative curvature, however, it will expand forever.
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A voyage to another star would require exact information on distances and properties of the stars. This lecture shows how astronomers measure the distance to nearby stars and how they determine their surface temperatures, which are the basis for stellar classification.