Electromagnetic Spectrum Lecture Standards Explain how objects in

Electromagnetic Spectrum Lecture

Standards • Explain how objects in the universe emit different electromagnetic radiation and how this information is used • Examine the role that NM research facilities play in current space exploration (e. g. , Very Large Array) • Understand how knowledge about the universe comes from evidence collected from advanced technology (e. g. , telescopes) • Describe wave propagation using amplitude, wavelength and frequency

Electromagnetic Radiation • Electromagnetic Radiation - another term for light. • It transfers energy and information from one place to another.

Electromagnetic Spectrum • The range of electromagnetic radiation: radio waves, infrared, visible, ultraviolet, x-rays and gamma rays. • These all differ in wavelength • They all travel the same speed in a vacuum: 300, 000 km/s or 186, 000 mi/s. This is the speed of light, denoted by c. • Snap your fingers • In the time it takes you to snap your fingers, light travels ¾ of the way around the earth.

The Electromagnetic Spectrum

Electromagnetic Spectrum • Radiation is the way in which energy is transmitted through space from one point to another without the need for any physical connection between the two locations. • Electromagnetic means that the energy is carried in the form of rapidly fluctuating electric and magnetic fields.

Electric & Magnetic Wave Fields

Electromagnetic Spectrum • • 1. 2. 3. Visible light is the wavelength that human eyes are sensitive to We experience sight when: Light enters the eye The cornea and lens focus it onto the retina An electrical impulse goes to the brain, giving us the sensation of sight

Wave Motion • All electromagnetic radiation travels through space in the form of waves. • Energy is transferred from one place to another without the movement of the material it’s traveling through. • Waves do not need a medium (i. e. , substance) to travel through.

Wave Motion • Draw the following wave and label its parts • This is a transverse wave Crest Resting point Wavelength Amplitude Trough • Frequency = # waves second

Wave Motion • Wavelength is measured in units of Ångstroms (Å) (older unit) or nanometers (nm) • There are 109 nm in 1 meter: • 109 = 1, 000, 000

Wave Motion • Visible wavelengths range from 400 – 700 nm or 4000 – 7000 Å. • Your eyes are most sensitive to the 550 nm, or 5500 Å wavelength. • This is yellow-green: the newer color of fire trucks and school crossing signs. • The sun emits most of its energy in this wavelength.

Parts of the Electromagnetic Spectrum • • • Radio Infrared Visible Ultraviolet X-rays Gamma rays

Radio Waves • Longest wavelengths, therefore lowest energy ü 1 cm to 108 m • Includes radar, microwave, AM, FM and TV

Radio Waves • Radio telescopes collect and concentrate radio waves • They are giant antennas • Radio waves were discovered in 1930 • By 1940, the radio sky was charted • Technology was developed because of WWII

Radio Waves • Radio telescopes can observe 24 hours a day • Can observe parts of the universe that can’t be seen optically ü Ex: black holes. Never observed before radio astronomy

Sgr. A: black hole at center of Milky Way Photo: UC Berkely, http: //www. berkeley. edu/news/media/releases/2002/10/23_bhole. html

Radio Waves • Radio telescopes have poor angular resolution ü Resolution = the ability to distinguish between objects that are close together. ü Higher resolution = better detail. • Interferometry –technique where two or more telescopes are put together to increase resolution. ü They look at the same object, in the same wavelength, at the same time

Radio Telescopes • VLA = Very Large Array ü Radio telescopes located on San Agustin Plains near Socorro, NM ü Located at 7000 ft and isolated in mountain ranges to block interference from other radio sources. ü World renowned astronomers come here from all over the world.

Radio Telescopes ü 28 antennas (27 working, one for replacing during repairs) ü Arranged in a Y-shaped configuration ü Each telescope is 25 meters in diameter (about length of classroom) and weighs 235 tons ü Receivers are cooled to -430 F to get rid of interference.

VLA 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

VLA Under Radio Sky Photo: NROA, http: //www. cv. nrao. edu/ ~abridle/images. html

Radio Telescopes • National Radio Astronomy Observatory, Green Bank, West Virginia ü World’s largest moveable radio telescope ü 43 m in diameter & 150 m tall (taller than Statue of Liberty) ü Original structure collapsed, has been rebuilt

Photo: APOD, http: //antwrp. gsfc. nasa. gov/apod/ap 020311. html

Radio Telescopes • Arecibo Observatory, Puerto Rico ü World’s largest radio telescope ü 300 m in diameter ü Surface spans nearly 20 acres

Photo: http: //www. evlbi. org/evlbi/te 024. html

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

Radio Telescopes • Very Long Baseline Array ü 10 radio telescopes spanning 5, 351 miles ü World’s largest and sharpest (you could be in Los Angeles and clearly read a street sign in New York City ü Used to observe quasars, black holes and stars in every stage of stellar life cycle

Very Long Baseline Array

Radio Telescopes • Atacama Large Millimeter/submillimeter Array (ALMA) (still being built) ü Highest array at 16, 500’ ü In Atacama desert, Chile ü At least 66 telescopes ü Maximum range = 71, 000 square feet of radio light collecting area ü Largest leap in telescope technology since Galileo first aimed a lens on the universe

ALMA

Infrared (IR) • Wavelengths are just longer than we can see without special goggles • Infrared radiation is heat (produced by many objects) • It is used in the medical field, police work, military…(night vision goggles)

Infrared (IR) • Infrared telescopes are placed in high, dry areas because Earth’s atmosphere interferes with IR radiation • Telescopes need to be cooled down close to absolute zero • Equipped with a bolometer, made of germanium, to detect the IR • Bolometer = device used to measure electromagnetic radiation

Infrared (IR) • Infrared telescopes can see through interstellar dust ü Ex: can see the center of Milky Way • Can be used during the day

Center of Milky Way: Spitzer

Orion Nebula in IR & Visible

Infrared (IR) • IR observatories in space (above Earth’s atmosphere): ü Spitzer Space Telescope – current IR telescope, launched in 2003

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

Visible Light • White light is made up of the colors red, orange, yellow, green, blue, indigo, violet. • Remember the acronym ROY G BIV • 400 -700 nm wavelengths • Sir Isaac Newton discovered this 300 years ago • The color is determined by the wavelength: ü Red has the longest wavelength ü Violet has the shortest wavelength • Observing in visible light is called optical astronomy

Ultraviolet (UV) • Wavelengths 400 nm down to a few nanometers • Causes sunburn and cancer • Helps produce vitamin D • Ozone protects Earth from most UV radiation, so UV studies must be done above Earth’s atmosphere

Ultraviolet (UV) • UV telescopes: ü Far Ultraviolet Explorer (FUSE) – launched in 1999 ü Galaxy Evolution Explorer (GALEX) – launched in 2003 ü Hubble Space Telescope has UV detectors

X-Rays • Wavelengths are a few nm to hundredths of a nm • Have medical uses • Blocked by Earth’s atmosphere, so observing done from space

X-Rays • X-Ray telescopes: ü Chandra X-Ray Observatory – launched in 1999 aboard the Columbia. Still in operation ü Nustar X-Ray Telescope – launched June 13, 2012 to image the sky in high energy x-rays

Chandra

W 49 b: Supernova: Chandra

Nustar

Gamma Rays • Shortest wavelength, therefore highest energy • Associated with radioactivity • Observing done from space

Gamma Rays • Telescopes count photons in a given direction ü Photon – packet of electromagnetic radiation (i. e. , particle of light) ü Photons are scarce, takes hours to days to capture one photon • Fermi Space Telescope – launched June 11, 2008