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Light, Astronomical Observations, and the Sun. Terms. Spectrum A range of something, e.g. colors Spectra Plural of spectrum Incandescent Hot enough to glow (emit visible light radiation). Terms. Wavelength ( λ ) Length of one wave from peak to peak Shorter wavelength = more energy

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terms
Terms
  • Spectrum
    • A range of something, e.g. colors
  • Spectra
    • Plural of spectrum
  • Incandescent
    • Hot enough to glow (emit visible light radiation)
terms1
Terms
  • Wavelength (λ)
    • Length of one wave from peak to peak
    • Shorter wavelength = more energy
    • For visible light
      • Shorter wavelength = BLUE
      • Longer wavelength = RED
terms2
Terms
  • Light-year
    • Distance traveled by light in one year
    • 5,900,000,000,000 miles
    • Measure of distance, not time
light astronomical observations the sun
Light, Astronomical Observations, & the Sun

PSCI 131: Light, Astronomical Observations, & The Sun

  • Signals From Space
  • Spectroscopy
  • The Doppler Effect
  • Optical Telescopes
  • Radio and Orbiting Telescopes
  • The Structure of the Sun
signals from space
Signals from Space

PSCI 131: Light, Astronomical Observations, & The Sun

  • The electromagnetic (EM) spectrum
    • Energy waves (radiation) emitted by matter
the em spectrum
The EM Spectrum

PSCI 131: Light, Astr. Observations, & The Sun – Signals from Space

em radiation from celestial objects
EM Radiation from Celestial Objects

PSCI 131: Light, Astr. Observations, & The Sun – Signals from Space

  • EM energy is emitted from many objects
    • Stars
    • Black holes
    • Supernovae (exploding stars)
    • Etc.
  • Not the same as reflected energy
    • Moons, planets, etc. reflect energy from stars
em radiation from celestial objects1
EM Radiation from Celestial Objects

PSCI 131: Light, Astr. Observations, & The Sun – Signals from Space

  • Emitted radiation can be collected and used to study the object
    • Telescopes: optical, radio, space-based
    • Spectroscopy
spectroscopy
Spectroscopy

PSCI 131: Light, Astr. Observations, & The Sun

spectroscopy1
Spectroscopy

PSCI 131: Light, Astronomical Observations, & The Sun

  • Using radiation from an object to learn about that object
  • Most astronomical observations can only use radiation
    • Most objects too far away to visit
visible light spectra
Visible Light Spectra

PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy

  • 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
visible light spectra1
Visible Light Spectra

PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy

(Low-temp)

(Incandescent)

CONTINUOUS

BRIGHT-LINE

DARK-LINE

visible light spectra2
Visible Light Spectra

PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy

  • 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
continuous spectrum
Continuous Spectrum

PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy

  • Shows surface temperature of object
  • Shows total energy emitted by object
continuous spectrum shows surface temp
Continuous Spectrum Shows Surface Temp

PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy

COOLER

HOTTER

continuous spectrum shows total energy
Continuous Spectrum Shows Total Energy

PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy

  • Proportional to fourth power of object’s surface temperature
    • Example: if Star B is twice as hot as Star A…
    • …Star B emits 2 x 2 x 2 x 2 = 16 times more energy that Star A
dark line spectrum
Dark-Line Spectrum

PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy

  • Light from star’s interior passes through gas composing star’s exterior

Interior

Exterior gases

dark line spectrum1
Dark-Line Spectrum

PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy

  • Shows what elements are present in object
  • Each element absorbs a unique pattern of visible light wavelengths

From: mail.colonial.net

dark line spectrum2
Dark-Line Spectrum

PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy

  • Shows what elements are present in object
  • Each element absorbs a unique pattern of visible light wavelengths

From: mail.colonial.net

bright line spectrum
Bright-Line Spectrum

PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy

  • Shows what elements are present in object
  • Each element emits a unique wavelength pattern when heated

From: intro.chem.okstate.edu

the doppler effect
The Doppler Effect

PSCI 131: Light, Astr. Observations, & The Sun

Sheldon’s Doppler Effect costume

the doppler effect1
The Doppler Effect

PSCI 131: Light, Astronomical Observations, & The Sun – Doppler Effect

  • Apparent shift in wavelength relative to a stationary observer

The Doppler Effect with sound waves. Longer apparent wavelength = lower frequency.

red and blue shift
Red and Blue Shift

PSCI 131: Light, Astronomical Observations, & The Sun – Doppler Effect

  • Light waves undergo Doppler Effect
red blue shifts change dark line spectra
Red/Blue Shifts Change Dark-Line Spectra

PSCI 131: Light, Astronomical Observations, & The Sun – Doppler Effect

  • Star moving away from Earth = RED shift
  • Star approaching Earth = BLUE shift
optical telescopes
Optical Telescopes

PSCI 131: Light, Astr. Observations, & The Sun

optical telescopes1
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
optical telescopes refracting
Optical Telescopes: Refracting

PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes

From: www.odec.ca

optical telescopes refracting1
Optical Telescopes: Refracting

PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes

  • 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
optical telescopes reflecting
Optical Telescopes: Reflecting

PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes

From: odec.ca

optical telescopes reflecting1
Optical Telescopes: Reflecting

PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes

  • 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

radio orbiting telescopes
Radio & Orbiting Telescopes

PSCI 131: Light, Astr. Observations, & The Sun

radio telescopes
Radio Telescopes

PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes

  • Gather radio waves from space
  • These signals are extremely faint
  • Collecting dish must be very large
radio telescopes1
Radio Telescopes

PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes

From: amazing-space.stsci.edu

radio telescope at arecibo puerto rico
Radio Telescope at Arecibo, Puerto Rico

PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes

World’s largest & most sensitive R.T.

Diameter: 1000 ft

Depth: 167 ft

Weight of receiver: 900 tons

orbiting telescopes
Orbiting Telescopes

PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes

  • Optical, radio, gamma-ray, X-ray, infrared
  • No atmospheric or human “noise”
the hubble space telescope
The Hubble Space Telescope

PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes

Type: Reflecting

Years in operation: 24

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

(76,700,000,000,000,000,000,000 miles)

From: nasa.gov

structure of the sun
Structure of the Sun

PSCI 131: Light, Astr. Observations, & The Sun

the sun s composition
The Sun’s Composition

PSCI 131: Light, Astr. Observations, & The Sun – The Sun

  • Form: gaseous
  • Density: slightly greater than water
  • Hydrogen: 90%
  • Helium: almost 10%
  • Other trace elements: less than 1%
the sun s emissions
The Sun’s Emissions

PSCI 131: Light, Astr. Observations, & The Sun – The Sun

  • The sun emits two things into space:
    • Radiation, including visible light
    • Solar wind, streams of protons & electrons
the sun s layers
The Sun’s Layers

PSCI 131: Light, Astr. Observations, & The Sun – The Sun

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

corona during solar eclipse
Corona (during solar eclipse)

PSCI 131: Light, Astr. Observations, & The Sun – The Sun’s Layers

From: mreclipse.com

chromosphere
Chromosphere

PSCI 131: Light, Astr. Observations, & The Sun – The Sun’s Layers

From: astroguyz.com

photosphere closeup view
Photosphere: closeup view

PSCI 131: Light, Astr. Observations, & The Sun – The Sun’s Layers

Source of visible light

Covered by granules

produced by convection

“Boiling” appearance

Movie: Visiting the photosphere for one hour

From: www.astronomynotes.com

the sun s engine
The Sun’s Engine

PSCI 131: Light, Astr. Observations, & The Sun – The Sun

  • Matter is converted to energy in the core
  • Nuclear fusion reactions
  • Hydrogen + hydrogen = helium + energy
    • 4 billion tons per second
  • E = mc2

c: speed of light (186,000 miles/second)