Astronomy 101 Notes January 21 2014 Introduction to Astronomy Expanding Universe Big Bang occurred 14 billion years ago Sequence of Events 1 Inflationary Era AU astronomical unit the distance between Earth and Sun Lightyear distance light travels in one year Galaxies are constantly moving away from center of universe linear equation the farther away the galaxy is the faster it is moving Evidence for Big Bang o Vastly increased size of universe from size of a proton o What changed High temperature energy is defined by temperature 2 Helium Synthesis Era 1 10 minutes after o Provided all helium in universe when protons fused with neutrons o Protons and neutrons become stable after universe cools 3 Radiation Era 400 000 years after o Electrons are no longer free but paired with protons o Universe is now transparent 4 Galaxy Formation 500 000 000 years after o Gravity pulls matter into clumps such as galaxies 5 Formation of Solar System 8 000 000 000 years after o Most gas collapsed to center making the sun o Planets formed out of leftover rotating cloud Temperature and Energy Energy emitted by moving atoms is manifested as temperature Can be measured using F C or Kelvin o Kelvin is the only scale where amount of energy is proportional to temperature Announcements Course site http www blogs umass edu astron101 Email Min Yun myun astro umass edu Class consists of 3 exams 1 final 1 homework grade o Worst out of these 5 is dropped at semester s end
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