light, astronomical observations, and the sun
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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
– For visible light• Shorter wavelength = BLUE• Longer wavelength = RED
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
• 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, Astronomical Observations, & The Sun
The EM SpectrumPSCI 131: Light, Astr. Observations, & The Sun – Signals from Space
EM Radiation from Celestial Objects
• 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
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 – Signals from Space
Spectroscopy
PSCI 131: Light, Astr. 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
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 SpectraPSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy
(Low-temp) (Incandescent)
CONTINUOUS DARK-LINE BRIGHT-LINE
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 TempPSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy
COOLER HOTTER
Continuous Spectrum Shows Total Energy
• 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
PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy
Dark-Line SpectrumPSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy
• Light from star’s interior passes through gas composing star’s exterior
Exterior gases
Interior
Dark-Line SpectrumPSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy
From: mail.colonial.net
• Shows what elements are present in object
• Each element absorbs a unique pattern of visible light wavelengths
Dark-Line SpectrumPSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy
From: mail.colonial.net
• Shows what elements are present in object
• Each element absorbs a unique pattern of visible light wavelengths
Bright-Line Spectrum• Shows what elements are present in object
• Each element emits a unique wavelength pattern when heated
PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy
From: intro.chem.okstate.edu
The Doppler Effect
PSCI 131: Light, Astr. Observations, & The Sun
Sheldon’s Doppler Effect costume
The Doppler Effect• Apparent shift in wavelength relative to a
stationary observer
PSCI 131: Light, Astronomical Observations, & The Sun – Doppler Effect
The Doppler Effect with sound waves. Longer apparent wavelength = lower frequency.
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, Astronomical Observations, & The Sun – Doppler Effect
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
Optical Telescopes: RefractingPSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes
From: www.odec.ca
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
Optical Telescopes: ReflectingPSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes
From: odec.ca
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
PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes
From: www.odec.ca
Radio & Orbiting Telescopes
PSCI 131: Light, Astr. Observations, & The Sun
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
PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes
From: amazing-space.stsci.edu
Radio Telescope at Arecibo, Puerto RicoPSCI 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• 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 TelescopePSCI 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
From: nasa.gov
(76,700,000,000,000,000,000,000 miles)
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
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
The Sun’s LayersPSCI 131: Light, Astr. Observations, & The Sun – The Sun
Modified from: visual.merriam-webster.com
1. CORONA
2. CHROMOSPHERE
3. PHOTOSPHERE
5. RADIATION ZONE
4. CONVECTION ZONE
6. CORE
Numbers are in order of increasing depth
PSCI 131: Light, Astr. Observations, & The Sun – The Sun’s Layers
From: mreclipse.com
Corona (during solar eclipse)
PSCI 131: Light, Astr. Observations, & The Sun – The Sun’s Layers
From: astroguyz.com
Chromosphere
PSCI 131: Light, Astr. Observations, & The Sun – The Sun’s Layers
From: www.astronomynotes.com
Photosphere: closeup view
Source of visible light
Covered by granules
produced by convection
“Boiling” appearance
Movie: Visiting the photosphere for one hour
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 = mc2
c: speed of light (186,000 miles/second)
PSCI 131: Light, Astr. Observations, & The Sun – The Sun
End of Light & The Sun Chapter