Final Exam Review Guide

Final Exam Review Guide - Astronomy Final Exam Review Age...

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Astronomy Final Exam Review Age of Universe •How Do we determine the age of the universe? can use distance measurements to determine the age of the universe expansion implies that the universe came into being at a single moment in time the inverse of the Hubble constant tells us approximately how long the universe has been expanding •What is the approximate age of the universe? 14 billion years Timeline of the Universe •When was most of the helium in the universe produced? Era of Nucleosynthesis- .001 sec after big bang neutrons could change into protons- couldn’t change back Universe became too cool to produce protons and neutrons- cooling allowed protons and neutrons to fuse into long lasting helium Evidence: we observe helium clouds •When did photons first start streaming freely across the universe? The Era of Nuclei- 5 minutes after big bang Universe to cool for fusion of H to He Universe consisted of a very hot plasma of hydrogen nuclei, helium nuclei, and electrons electrons first combined with nuclei to make atoms cosmic microwave background- The radiation left over from the Big Bang No direct evidence during this time •What is the primary evidence in favor of the big bang theory? Leftover radiation from the Big Bang- cosmic Microwave Background The theory correctly predicts the composition of the universe (the abundance of helium and other light elements) Darkness of the night sky- Olber’s paradox- if the universe were infinite, unchanging, and everywhere the same- the entire night sky would be as bright as the sun we can only see the stars within our observable universe •Approximately when did the first galaxies form? Era of Galaxies- universe was 1 billion years old present day era directly observable •When did the solar system form? 4.6 Billion years ago •How do we determine the age of the solar system? hubbles law velocity= hubbles constant x distance Contents of the Universe •What is the typical composition of stars and gas clouds in galaxies?
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Star are born in cold, dense clouds of gas whose pressure cannot resist gravitational contraction Molecular clouds- the coldest, densest clouds that stars are formed in a star is born when gravity causes a cloud of interstellar gas to contract to the point at which the central object becomes hot enough to sustain nuclear fusion Star-Gas-Star Cycle Hot ionized gas Warm neutral gas Cool Neutral gas Molecular clouds- star formation Molecular cores- Star formation Hot, massive stars are signs of a region of active star formation •How are elements heavier that hydrogen and helium made?
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This note was uploaded on 01/18/2012 for the course ADV 260 taught by Professor Issacson during the Fall '08 term at Michigan State University.

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Final Exam Review Guide - Astronomy Final Exam Review Age...

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