Light Astronomical Observations and the Sun PSCI 131
Light, Astronomical Observations, and the Sun
PSCI 131: Light, Astronomical Observations, & The Sun Light, Astronomical Observations, & the Sun • • • Signals From Space Spectroscopy The Doppler Effect Optical Telescopes Radio and Orbiting Telescopes The Structure of the Sun
PSCI 131: Light, Astronomical Observations, & The Sun Signals from Space • The electromagnetic (EM) spectrum – Energy waves (radiation) emitted by matter
PSCI 131: Light, Astr. Observations, & The Sun – Signals from Space The EM Spectrum
PSCI 131: Light, Astr. Observations, & The Sun – Signals from Space EM Radiation from Celestial Objects • EM energy is emitted from many objects – Stars, black holes, supernovas (exploding stars), etc. • Not the same as reflected energy – Moons, planets, etc. reflect light energy from stars
PSCI 131: Light, Astr. Observations, & The Sun – Signals from Space EM Radiation from Celestial Objects • Emitted radiation can be collected and used to study the object – Telescopes: optical, radio, space-based – Spectroscopy
PSCI 131: Light, Astr. Observations, & The Sun Spectroscopy
PSCI 131: Light, Astronomical Observations, & The Sun Spectroscopy • Using radiation from an object to learn about that object • Most astronomical observations can only use radiation – Most objects too far away to visit
PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy Visible Light Spectra • Visible light can be split into its component wavelengths (colors) • Creates continuous, bright-line, and dark-line spectra • Spectra can give key information about the object the light came from
PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy Visible Light Spectra (Low-temp) CONTINUOUS DARK-LINE (Incandescent) BRIGHT-LINE
PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy Visible Light Spectra • Visible light can be split into its component wavelengths (colors) • Creates continuous, bright-line, and dark-line spectra • Spectra can give key information about the object the light came from
PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy Continuous Spectrum • Shows surface temperature of object • Shows total energy emitted by object
PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy Continuous Spectrum Shows Surface Temp exaggerated COOLER HOTTER
PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy Continuous Spectrum Shows Total Energy • Proportional to fourth power of object’s surface temperature – Example: if Star B is five times as hot as Star A… – …Star B emits 54, or 5 x 5 x 5 = 625 times more energy that Star A
PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy Dark-Line Spectrum • Light from star’s interior passes through gas composing star’s exterior Interior Exterior gases
PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy Dark-Line Spectrum • Shows what elements are present in object • Each element absorbs a unique pattern of visible light wavelengths From: mail. colonial. net
PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy Dark-Line Spectrum • Shows what elements are present in object • Each element absorbs a unique pattern of visible light wavelengths From: mail. colonial. net
PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy Bright-Line Spectrum • Shows what elements are present in object • Each element emits a unique wavelength pattern when heated From: intro. chem. okstate. edu
PSCI 131: Light, Astronomical Observations, & The Sun – Doppler Effect The Doppler Effect • Apparent shift in wavelength relative to a stationary observer The Doppler Effect with sound waves. Longer apparent wavelength = lower frequency.
PSCI 131: Light, Astronomical Observations, & The Sun – Doppler Effect Red and Blue Shift • Light waves undergo Doppler Effect
PSCI 131: Light, Astronomical Observations, & The Sun – Doppler Effect Red/Blue Shifts Change Dark-Line Spectra • Star moving away from Earth = RED shift • Star approaching Earth = BLUE shift
PSCI 131: Light, Astr. Observations, & The Sun Optical Telescopes
PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes • Gather visible light radiation • Concentrate it at a focal point, creating magnified image • Two types – Refracting – Reflecting
PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes: Refracting From: www. odec. ca
PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes: Refracting • Advantages – Inexpensive – Lens doesn’t have to be perfect to make a decent image • Drawbacks – Chromatic aberration reduces image quality, limits maximum telescope size – Chromatic aberration: “halo” of color around image caused by refracted light
PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes: Reflecting From: odec. ca
PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes: Reflecting • Advantages – No chromatic aberration – Can be very large, so higher magnification • Drawbacks – More expensive – Tiny flaws in mirror can greatly reduce image quality From: www. odec. ca
PSCI 131: Light, Astr. Observations, & The Sun Radio & Orbiting Telescopes
PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes Radio Telescopes • Gather radio waves from space • These signals are extremely faint • Collecting dish must be very large
PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes Radio Telescopes From: amazing-space. stsci. edu
PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes Radio Telescope at Arecibo, Puerto Rico World’s largest & most sensitive R. T. Diameter: 1000 ft Depth: 167 ft Weight of receiver: 900 tons
PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes Orbiting Telescopes • Optical, radio, gamma-ray, X-ray, infrared • No atmospheric or human “noise”
PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes The Hubble Space Telescope Type: Reflecting Years in operation: 25 Orbit height: 347 miles Orbital speed: 25, 000 ft/sec Length: 43 ft Mirror diameter: 7. 9 ft Farthest object observed: 13 billion light years away (76, 700, 000, 000 miles) From: nasa. gov
PSCI 131: Light, Astr. Observations, & The Sun Structure of the Sun
PSCI 131: Light, Astr. Observations, & The Sun – The Sun’s Composition • Form: gaseous • Density: slightly greater than water • Hydrogen: 90% • Helium: almost 10% • Other trace elements: less than 1%
PSCI 131: Light, Astr. Observations, & The Sun – The Sun’s Emissions • The sun emits two things into space: – Radiation, including visible light – Solar wind, streams of protons & electrons
PSCI 131: Light, Astr. Observations, & The Sun – The Sun’s Layers Numbers are in order of increasing depth 2. CHROMOSPHERE 5. RADIATION ZONE 4. CONVECTION ZONE 6. CORE 3. PHOTOSPHERE 1. CORONA Modified from: visual. merriam-webster. com
PSCI 131: Light, Astr. Observations, & The Sun – The Sun’s Layers Corona (during solar eclipse) From: mreclipse. com
PSCI 131: Light, Astr. Observations, & The Sun – The Sun’s Layers Chromosphere From: astroguyz. com
PSCI 131: Light, Astr. Observations, & The Sun – The Sun’s Layers Photosphere: closeup view Source of visible light Covered by granules produced by convection “Boiling” appearance Photosphere time lapse From: www. astronomynotes. com
PSCI 131: Light, Astr. Observations, & The Sun – The Sun’s Engine • Matter is converted to energy in the core • Nuclear fusion reactions • Hydrogen + hydrogen = helium + energy – 4 billion tons per second • E = mc 2 c: speed of light (186, 000 miles/second)
End of Light & The Sun Chapter
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