NS102 Lavalli - JSAs 7-10 (4-15-08)

NS102 Lavalli - JSAs 7-10 (4-15-08) - JSA 7 : Modern...

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JSA 7 : Modern Astronomy Astronomy After the Scientific Revolution o Galileo proved that the universe is not Aristotelian using a refracting telescope o Newton provided physics supporting Kepler and the reflecting telescope o Modern astronomy uses physics and technology to observe the entire universe Exploring the universe after Newton o Much bigger telescopes (e.g. Hubble) o Spectrometry: distinguishing “colors” Spectrometry o Colors: wavelengths and frequencies Spectrometry from Earth o Visible spectrum: 400-700nm o 1m+ : visible radio waves
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Observation o Earth-bound (e.g. Keck telescope array in Hawaii) o Extraterrestrial orbiters (Voyagers, New Horizons ) o Earth Orbiters (Hubble) Distance in Space o Astronomical Unit: AU = Earth-Sun distance Equals 91 million miles (1.5 x10 8 Km) Most useful within the solar system Nearest star ( Proxima Centauri ) at 26,800 AU. o Light Year: ly = distance light goes in 1 year 1 light year = 6 trillion miles (9.5 x 10 12 Km) Most useful within the galaxy o Proxima Centauri is 4.24 light years away. How large is Universe? o Roughly 14 billion light years in extent. o Contains 125 billion galaxies o Each galaxy has 100 billion stars and is roughly ≤ 100,000 light years across (size depends on galaxy type) Spiral Galaxies o All about the same size, 100,000 light years in diameter o Apparent sizes give relative distances (will use this fact in lab this week) Elliptical Galaxies o up to 100,000 light years across Irregular Galaxies o “Only” about 30,000 light years across. o Each has about 100 Million stars
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JSA 8: The Big Bang Every galaxy is moving away from the Local Group (where Earth is)! Speed between two objects (e.g. Earth & a distant galaxy) is found from the Doppler Effect. Doppler Effect o If an object moves away from an observer, its light is shifted to lower frequencies. o (longer wavelength = red shift) o If an object moves toward an observer, its light is shifted to higher frequencies. o (shorter wavelength = blue shift) Equasions o If a galaxy moves away from Earth, its wavelength λ of light is red shifted Δλ: Δλ = v λ c o v: speed of galaxy relative to Earth o c: speed of light o The farther a galaxy is, the faster it moves away from us. o Hubble’s Law (1920s) v = H * d v: speed of galaxy H: Hubble’s constant d: distance to galaxy Big Bang Theory o All energy and matter in the universe came from a “primeval fireball” about 10-15 billion years ago. (Recent best estimate: 13.7 billion years ago)
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o Universe has expanded ever since. o First proponents: Georges Lemaître, George Gamow Georges Lemaître (1894-1966) o Belgian, Roman Catholic priest. o
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NS102 Lavalli - JSAs 7-10 (4-15-08) - JSA 7 : Modern...

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