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 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 – 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 Spectra PSCI 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 Temp PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy COOLERHOTTER exaggerated

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 5 4, 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 PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy Light from star’s interior passes through gas composing star’s exterior Exterior gases Interior

Dark-Line Spectrum PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy From: mail.colonial.net mail.colonial.net Shows what elements are present in object Each element absorbs a unique pattern of visible light wavelengths

Dark-Line Spectrum PSCI 131: Light, Astronomical Observations, & The Sun - Spectroscopy From: mail.colonial.net 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.eduintro.chem.okstate.edu

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

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

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: Reflecting PSCI 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:

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 amazing-space.stsci.edu

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 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 PSCI 131: Light, Astr. Observations, & The Sun – Radio & Space Telescopes 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 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 Layers PSCI 131: Light, Astr. Observations, & The Sun – The Sun Modified from: visual.merriam-webster.comvisual.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: 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 = mc 2 c: speed of light (186,000 miles/second) PSCI 131: Light, Astr. Observations, & The Sun – The Sun

End of Light & The Sun Chapter