Electromagnetic Spectrum Lecture. Standards Explain how objects in the universe emit different...

Electromagnetic Spectrum LectureElectromagnetic Spectrum Lecture

StandardsStandards

• Explain how objects in the universe emit Explain how objects in the universe emit different electromagnetic radiation and how different electromagnetic radiation and how this information is usedthis information is used

• Examine the role that NM research facilities Examine the role that NM research facilities play in current space exploration (e.g., Very play in current space exploration (e.g., Very Large Array)Large Array)

• Understand how knowledge about the Understand how knowledge about the universe comes from evidence collected from universe comes from evidence collected from advanced technology (e.g., telescopes)advanced technology (e.g., telescopes)

• Describe wave propagation using amplitude, Describe wave propagation using amplitude, wavelength and frequencywavelength and frequency

Electromagnetic RadiationElectromagnetic Radiation

• Electromagnetic Radiation - Electromagnetic Radiation - another term for light.

• It transfers energy energy and information information from one place to another.

Electromagnetic SpectrumElectromagnetic Spectrum

• The range of electromagnetic The range of electromagnetic radiationradiation: : radio waves, radio waves, infraredinfrared, visible, , visible, ultravioletultraviolet, , x-rays and x-rays and gammagamma rays. rays.

• These all differ in These all differ in wavelengthwavelength• They all travel the same They all travel the same speedspeed in a in a

vacuum: 300,000 km/s or 186,000 mi/s. vacuum: 300,000 km/s or 186,000 mi/s. This is the speed of This is the speed of lightlight, denoted by , denoted by cc..

• Snap your fingersSnap your fingers• In the In the timetime it takes you to snap your it takes you to snap your

fingers, light travels fingers, light travels ¾¾ of the way of the way around the around the earthearth..

The Electromagnetic SpectrumThe Electromagnetic Spectrum


• Radiation is the way in which Radiation is the way in which energyenergy is is transmitted through space from one transmitted through space from one point to another without the need for point to another without the need for any physical connection between the any physical connection between the two locations.two locations.

• Electromagnetic means that the energy Electromagnetic means that the energy is carried in the form of rapidly is carried in the form of rapidly fluctuating fluctuating electricelectric and and magneticmagnetic fields. fields.

Electric & Magnetic Wave FieldsElectric & Magnetic Wave Fields


• VisibleVisible light is the wavelength that light is the wavelength that human human eyeseyes are sensitive to are sensitive to

• We experience sight when:We experience sight when:

1.1. Light enters the eyeLight enters the eye

2.2. The cornea and lens focus it onto the The cornea and lens focus it onto the retinaretina

3.3. An electrical impulse goes to the brain, An electrical impulse goes to the brain, giving us the sensation of sightgiving us the sensation of sight

Wave MotionWave Motion

• All electromagnetic radiation travels All electromagnetic radiation travels through space in the form of through space in the form of waveswaves..

• Energy is Energy is transferredtransferred from one place to from one place to another without the movement of the another without the movement of the material it’s traveling through.material it’s traveling through.

• Waves do not need a medium (i.e., Waves do not need a medium (i.e., substance) to travel through.substance) to travel through.

Wave MotionWave Motion• Draw the following wave and label its partsDraw the following wave and label its parts• This is a This is a transversetransverse wave wave

Crest

Trough

Wavelength

Resting point

• FrequencyFrequency = # waves second

Amplitude


• Wavelength is measured in units of Wavelength is measured in units of Ångstroms (Å) (older unit) or Ångstroms (Å) (older unit) or nanometersnanometers (nm) (nm)

• There are 10There are 1099 nm in 1 meter: nm in 1 meter:

• 101099 = 1,000,000,000 = 1,000,000,000


• Visible wavelengths range from Visible wavelengths range from 400400 – – 700700 nm or 4000 – 7000 nm or 4000 – 7000 Å.Å.

• Your eyes are most sensitive to the 550 Your eyes are most sensitive to the 550 nm, or 5500 Å wavelength.nm, or 5500 Å wavelength.

• This is This is yellow-greenyellow-green: the newer color of : the newer color of fire trucks and school crossing signs.fire trucks and school crossing signs.

• The The sunsun emits most of its emits most of its energyenergy in this in this wavelength.wavelength.

Parts of the Electromagnetic SpectrumParts of the Electromagnetic Spectrum

• RadioRadio

• InfraredInfrared

• VisibleVisible

• UltravioletUltraviolet

• X-raysX-rays

• Gamma raysGamma rays

RadioRadio Waves Waves

• LongestLongest wavelengths, therefore wavelengths, therefore lowestlowest energyenergy

1 cm to 101 cm to 1088 m m

• Includes radar, Includes radar, microwavemicrowave, AM, , AM, FMFM and and TVTV

Radio WavesRadio Waves

• Radio Radio telescopestelescopes collect and collect and concentrate radio wavesconcentrate radio waves

• They are giant They are giant antennasantennas

• Radio waves were discovered in Radio waves were discovered in 19301930

• By 1940, the radio sky was chartedBy 1940, the radio sky was charted

• Technology was developed because of Technology was developed because of WWIIWWII


• Radio telescopes can observe Radio telescopes can observe 2424 hours hours a daya day

• Can observe parts of the universe that Can observe parts of the universe that can’t be seen opticallycan’t be seen optically

Ex: Ex: blackblack holes. Never observed before holes. Never observed before radio astronomyradio astronomy

SgrA: black hole at center of Milky WaySgrA: black hole at center of Milky Way

Photo: UC Berkely, http://www.berkeley.edu/news/media/releases/2002/10/23_bhole.html


• Radio telescopes have poor Radio telescopes have poor angularangular resolution resolution

ResolutionResolution = the ability to distinguish = the ability to distinguish between objects that are close together.between objects that are close together.

HigherHigher resolution = better resolution = better detaildetail..• InterferometryInterferometry –technique where –technique where twotwo or or

more telescopes are put together to more telescopes are put together to increaseincrease resolution. resolution.

They look at the same They look at the same objectobject, in the , in the same same wavelengthwavelength, at the same , at the same timetime

Radio TelescopesRadio Telescopes

• VLAVLA = Very Large Array = Very Large ArrayRadio telescopes located on San Radio telescopes located on San

Agustin Plains near Agustin Plains near SocorroSocorro, NM, NMLocated at Located at 70007000 ft and isolated in ft and isolated in

mountain ranges to mountain ranges to blockblock interference interference from other radio sources.from other radio sources.

World renowned astronomers come World renowned astronomers come here from all over the world.here from all over the world.


2828 antennas (27 working, one for antennas (27 working, one for replacing during repairs)replacing during repairs)

Arranged in a Arranged in a YY-shaped configuration-shaped configurationEach telescope is 25 meters in diameter Each telescope is 25 meters in diameter

(about length of classroom) and weighs (about length of classroom) and weighs 235 tons235 tons

Receivers are cooled to -430Receivers are cooled to -430 F to get F to get rid of interference.rid of interference.

VLA Y-Shaped ConfigurationVLA Y-Shaped Configuration

Photo: http://bigbro.biophys.cornell.edu/~toombes/Science_Education/Crystal_Radio/VLA.jpg

Photos: L. Brown, June 2007

Photo: L. Brown, June 2007

Photo: NROA, http://www.cv.nrao.edu/~abridle/images.html

VLA Under VLA Under Radio SkyRadio Sky


• National Radio Astronomy Observatory, National Radio Astronomy Observatory, GreenGreen Bank, West Virginia Bank, West Virginia

World’s largest World’s largest moveablemoveable radio radio telescopetelescope

43 m in diameter & 150 m tall (taller 43 m in diameter & 150 m tall (taller than Statue of Liberty)than Statue of Liberty)

Original structure collapsed, has been Original structure collapsed, has been rebuiltrebuilt

Photo: APOD, http://antwrp.gsfc.nasa.gov/apod/ap020311.html


• AreciboArecibo Observatory, Puerto Rico Observatory, Puerto RicoWorld’s World’s largestlargest radio telescope radio telescope300 m in diameter300 m in diameterSurface spans nearly 20 acresSurface spans nearly 20 acres

Photo: http://www.evlbi.org/evlbi/te024/te024.html

Photo: http://commons.wikimedia.org/wiki/Image:Arecibo_Observatory_Aerial.jpg


• Very Long Very Long Baseline Baseline ArrayArray10 radio telescopes spanning 5,351 miles10 radio telescopes spanning 5,351 milesWorld’s World’s largest largest and and sharpest sharpest (you could be (you could be

in Los Angeles and clearly read a street in Los Angeles and clearly read a street sign in New York Citysign in New York City

Used to observe Used to observe quasarsquasars, black holes and , black holes and stars stars in every stage of stellar life cyclein every stage of stellar life cycle

Very Long Baseline ArrayVery Long Baseline Array

Radio TelescopesRadio Telescopes• Atacama Atacama Large Millimeter/submillimeter Large Millimeter/submillimeter

Array (ALMA) (still being built)Array (ALMA) (still being built)Highest Highest array at 16,500’ array at 16,500’ In Atacama desert, ChileIn Atacama desert, ChileAt least At least 66 66 telescopestelescopesMaximum range = 71,000 square feet of Maximum range = 71,000 square feet of

radio light collecting arearadio light collecting areaLargest Largest leap leap in telescope technology since in telescope technology since

Galileo first aimed a lens on the universeGalileo first aimed a lens on the universe

ALMAALMA

InfraredInfrared (IR) (IR)

• Wavelengths are just longer than we Wavelengths are just longer than we can see without special gogglescan see without special goggles

• Infrared radiation is Infrared radiation is heatheat (produced by (produced by many objects)many objects)

• It is used in the It is used in the medicalmedical field, field, policepolice work, military…(night vision goggles)work, military…(night vision goggles)

Infrared (IR)Infrared (IR)

• Infrared telescopes are placed in high, Infrared telescopes are placed in high, drydry areas because Earth’s areas because Earth’s atmosphereatmosphere interferes with IR radiationinterferes with IR radiation

• Telescopes need to be cooled down Telescopes need to be cooled down close to close to absoluteabsolute zero zero

• Equipped with a bolometer, made of Equipped with a bolometer, made of germaniumgermanium, to detect the IR, to detect the IR

• BolometerBolometer = device used to measure = device used to measure electromagnetic radiationelectromagnetic radiation


• Infrared telescopes can see through Infrared telescopes can see through interstellar interstellar dustdust

Ex: can see the Ex: can see the centercenter of Milky Way of Milky Way

• Can be used during the dayCan be used during the day

Center of Milky Way: SpitzerCenter of Milky Way: Spitzer

Orion Nebula in IR & VisibleOrion Nebula in IR & Visible


• IR observatories in space (above IR observatories in space (above Earth’s atmosphere):Earth’s atmosphere):

SpitzerSpitzer Space Telescope – current IR Space Telescope – current IR telescope, launched in 2003telescope, launched in 2003

Spitzer and Milky WaySpitzer and Milky Way

Photo: NASA, http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=1546

VisibleVisible Light Light• White light is made up of the colors White light is made up of the colors redred, ,

orangeorange, , yellowyellow, , green,green, blueblue, , indigoindigo, , violetviolet..• Remember the acronym ROY G BIVRemember the acronym ROY G BIV• 400 -700 nm wavelengths400 -700 nm wavelengths• Sir Isaac Sir Isaac NewtonNewton discovered this 300 years discovered this 300 years

agoago• The The colorcolor is determined by the is determined by the wavelengthwavelength::RedRed has the has the longestlongest wavelength wavelengthVioletViolet has the has the shortestshortest wavelength wavelength• Observing in visible light is called Observing in visible light is called opticaloptical

astronomyastronomy

UltravioletUltraviolet (UV) (UV)

• Wavelengths 400 nm down to a few Wavelengths 400 nm down to a few nanometersnanometers

• Causes Causes sunburnsunburn and and cancercancer

• Helps produce vitamin Helps produce vitamin DD

• Ozone protects Earth from most UV Ozone protects Earth from most UV radiation, so UV studies must be done radiation, so UV studies must be done aboveabove Earth’s atmosphere Earth’s atmosphere

Ultraviolet (UV)Ultraviolet (UV)

• UV telescopes:UV telescopes:Far Far UltravioletUltraviolet Explorer (FUSE) – launched Explorer (FUSE) – launched

in 1999in 1999Galaxy Evolution Explorer (Galaxy Evolution Explorer (GALEXGALEX) – ) –

launched in 2003launched in 2003Hubble Space Telescope has UV detectorsHubble Space Telescope has UV detectors

XX--RaysRays

• Wavelengths are a few nm to Wavelengths are a few nm to hundredths of a nmhundredths of a nm

• Have Have medicalmedical uses uses

• Blocked by Earth’s atmosphere, so Blocked by Earth’s atmosphere, so observing done from observing done from spacespace

X-RaysX-Rays

• X-Ray telescopes:X-Ray telescopes:ChandraChandra X-Ray Observatory – launched X-Ray Observatory – launched

in 1999 aboard the Columbia. Still in in 1999 aboard the Columbia. Still in operationoperation

Nustar Nustar X-Ray Telescope – launched X-Ray Telescope – launched June 13, 2012 to image the sky in high June 13, 2012 to image the sky in high energy x-raysenergy x-rays

ChandraChandra

W49b: Supernova: ChandraW49b: Supernova: Chandra

NustarNustar

GammaGamma Rays Rays

• ShortestShortest wavelength, therefore wavelength, therefore highesthighest energyenergy

• Associated with Associated with radioactivityradioactivity

• Observing done from Observing done from spacespace

Gamma RaysGamma Rays

• Telescopes count photons in a given directionTelescopes count photons in a given direction PhotonPhoton – packet of electromagnetic radiation (i.e., – packet of electromagnetic radiation (i.e.,

particle of light)particle of light) Photons are scarce, takes hours to days to Photons are scarce, takes hours to days to

capture one photoncapture one photon• FermiFermi Space Telescope – launched June 11, Space Telescope – launched June 11,

20082008

Artists illustration Artists illustration of Fermi Space of Fermi Space TelescopeTelescope

Photo: http://www.msnbc.msn.com/id/26408952/

Moon in Gamma: CGROMoon in Gamma: CGRO

Photo: http://www.answers.com/topic/gamma-ray?cat=health

The Sky in Many WavelengthsThe Sky in Many Wavelengths

Slide Show Slide Show

Milky Way in Visible Light

Photo: University of Washington, http://www.astro.washington.edu/labs/clearinghouse/lecture/pix.html

Milky Way in Radio: 73 cm wavelength

Photo: Washington University,http://www.astro.washington.edu/labs/clearinghouse/lecture/pix.html

Milky Way in Radio: 21 cm wavelength

Photo: Washington University,http://www.astro.washington.edu/labs/clearinghouse/lecture/pix.html

Milky Way in Microwaves: COBEMilky Way in Microwaves: COBE

Galactic Center in RadioGalactic Center in Radio

Photo: UC San Diego, http://cassfos02.ucsd.edu/public/tutorial/images/gc_1meter.jpg

Milky Way in IR: IRASMilky Way in IR: IRASPhoto: Caltech, http://www.ipac.caltech.edu/Outreach/Gallery/IRAS/IRAS_allsky_big.jpg

Photo: http://www.astro.livjm.ac.uk/courses/phys134/cosmo.html

Sky in UltravioletSky in Ultraviolet Photo: http://minho.kasi.re.kr/iCAP/ImageGallery/0705.AllSky.html

X-Ray Sky: ROSATX-Ray Sky: ROSATPhoto: APOD, http://zuserver2.star.ucl.ac.uk/~apod/apod/ap961008.html

Gamma Ray SkyGamma Ray Sky Photo: http://www.mpi-hd.mpg.de/hfm/HESS/public/physics/allsky1_egret.gif

11stst Light for Fermi Gamma Ray Light for Fermi Gamma Ray Telescope, 8-26-08Telescope, 8-26-08

Milky Way in Multiple WavelengthsMilky Way in Multiple Wavelengths

Electromagnetic Spectrum Lecture. Standards Explain how objects in the universe emit different...

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