Khan Academy on a Stick
Stars, black holes and galaxies
Our universe is defined by stars. This topic explores how they came to be and where they end up. This includes a discussion of black holes and galaxies.
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Birth of stars
Birth of Stars
- Accreting mass due to gravity simulation
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Becoming a red giant
Becoming a Red Giant
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White and black dwarfs
White and Black Dwarfs
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Star field and nebula images
Star Field and Nebula Images
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Lifecycle of massive stars
Lifecycle of Massive Stars
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Supernova (supernovae)
Supernova (Supernovae)
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Supernova clarification
Supernova clarification
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Black holes
Black Holes
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Supermassive black holes
Supermassive Black Holes
Life and death of stars
Stars begin when material drifting in space condenses due to gravity to be dense enough for fusion to occur. Depending on the volume and make-up of this material, the star could then develop into very different things--from supernovae, to neutron stars, to black holes. This tutorial explores the life of stars and will have you appreciating the grand weirdness of our reality.
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Quasars
Quasars
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Quasar correction
Quasar Correction
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Galactic collisions
Collision of the Milky Way Galaxy with Andromeda (forming "Milkomeda")
Quasars and galactive collisions
Quasars are the brightest objects in the universe. The gamma rays from them could sterilize a solar system (i.e. obliterate life). What do we think these objects are? Why don't we see any close by (which we should be thankful for)? Could they tell us what our own galaxy may have been like 1 billion or so years ago?
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Parallax in observing stars
Parallax in Observing Stars
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Stellar parallax
Another version of the stellar parallax introduction
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Stellar distance using parallax
Stellar Distance Using Parallax
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Stellar parallax clarification
Stellar Parallax Clarification
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Parsec definition
Parsec Definition
Stellar parallax
We've talked a lot about distances to stars, but how do we know? Stellar parallax--which looks at how much a star shifts in the sky when Earth is at various points in its orbit--is the oldest technique we have for measuring how far stars are. It is great for "nearby" stars even with precise instruments (i.e, in our part of our galaxy). To measure distance further, we have to start thinking about Cepheid variables (other tutorial).
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Cepheid variables 1
Cepheid Variables 1
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Why cepheids pulsate
Why Cepheids Pulsate
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Why gravity gets so strong near dense objects
Why Gravity Gets So Strong Near Dense Objects
Cepheid variables
Stellar parallax can be used for "nearby" stars, but what if we want to measure further out? Well this tutorial will expose you to a class of stars that helps us do this. Cepheids are large, bright, variable stars that are visible in other galaxies. We know how bright they should be and can gauge how far they are by how bright they look to us.