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Lecture 14

Astronomy Lecture 14.docx

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Patrick Mc Graw

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Astronomy Lecture 14 Scientific Method - Science is a systematic way to investigate the physical world Observations of the solar system - Common plane, directions of revolution and rotation - Two types of planets in the solar system - Two types of space debris - Radioactive dating The Big Bang Theory - 1. Making hydrogen and helium – 15min - 2. The universe to become transparent (400,000 years) - 3. First stars form – 4 mil years st - 4. 1 galaxy – 1 bil years, - 5. First and second generations of stars to enrich the universe with the other elements - 9 bil years. Star Formation - Observation – the visible surface of the sun and molecular clouds have the same composition - Hypothesis – the sun formed within a large, cool, rotating molecular cloud - Temperature – 10k, radius – 4k to 40k AU - If the gas in the cloud is compressed and become clumpy – the force of gravity on other gas particles increases – more gas is attracted - This core of gas continually grows hotter and denser until a star is born The solar nebula theory - Observation- the sun and all the contents of the solar system have a common age - Solar system bodies share common rotations and revolution in the same plane - Hypothesis 0 the planets formed in a rotating disk of gas and dust around a newly formed star. How does a cloud make a disk? - Gravity from the forming star pulls the particles inward - The rotation of the particles increases as they fall inwards because of conservation of angular momentum - Angular momentum – something is rotating and it is hard to stop it - What happens when the masses moves toward the axis of rotation- it moves faster - Particles above and below the star collide in the middle; this ends up making a flattened disk - Reminds of a galaxy - Prediction – if all stars form like this, there should be disks ( and planets) around most other stars Different materials at different distances - Observation – two types of planets - Higher densities closer to the Sun - The solar nebula wa
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