Light, Astronomical Observations, and the Sun

Light, Astronomical Observations, & 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

Signals from Space The electromagnetic (EM) spectrum 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

EM Radiation from Celestial Objects 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

EM Radiation from Celestial Objects 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

Spectroscopy Using radiation from an object to learn about that object 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) (Incandescent) CONTINUOUS BRIGHT-LINE DARK-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

Continuous Spectrum Shows surface temperature of object PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy Continuous Spectrum Shows surface temperature of object Shows total energy emitted by object

Continuous Spectrum Shows Surface Temp PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy Continuous Spectrum Shows Surface Temp exaggerated COOLER HOTTER

Continuous Spectrum Shows Total Energy 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 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

Dark-Line Spectrum Shows what elements are present in object 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 

Dark-Line Spectrum Shows what elements are present in object 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 

Bright-Line Spectrum Shows what elements are present in object 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.

Red and Blue Shift Light waves undergo Doppler Effect PSCI 131: Light, Astronomical Observations, & The Sun – Doppler Effect Red and Blue Shift Light waves undergo Doppler Effect

Red/Blue Shifts Change Dark-Line Spectra 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

Optical Telescopes Gather visible light radiation PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes Optical Telescopes Gather visible light radiation Concentrate it at a focal point, creating magnified image Two types Refracting Reflecting

Optical Telescopes: Refracting PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes Optical Telescopes: Refracting From: www.odec.ca 

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

Optical Telescopes: Reflecting PSCI 131: Light, Astr. Observations, & The Sun – Optical Telescopes Optical Telescopes: Reflecting From: odec.ca

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

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

Radio Telescopes Gather radio waves from space 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 

Radio Telescope at Arecibo, Puerto Rico 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

Orbiting Telescopes Optical, radio, gamma-ray, X-ray, infrared PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes Orbiting Telescopes Optical, radio, gamma-ray, X-ray, infrared No atmospheric or human “noise”

The Hubble Space Telescope 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 (76,700,000,000,000,000,000,000 miles) From: nasa.gov

PSCI 131: Light, Astr. Observations, & The Sun Structure of the Sun

The Sun’s Composition Form: gaseous PSCI 131: Light, Astr. Observations, & The Sun – The Sun The Sun’s Composition Form: gaseous Density: slightly greater than water Hydrogen: 90% Helium: almost 10% Other trace elements: less than 1%

The Sun’s Emissions The sun emits two things into space: 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 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

Corona (during solar eclipse) 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

Photosphere: closeup view 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

The Sun’s Engine Matter is converted to energy in the core PSCI 131: Light, Astr. Observations, & The Sun – 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 = mc2 c: speed of light (186,000 miles/second)

End of Light & The Sun Chapter