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 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 = 1,000,000,000

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 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 Ex: black holes. Never observed before radio astronomy

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

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

Radio Telescopes 28 antennas (27 working, one for replacing during repairs) Arranged in a Y-shaped configuration Each telescope is 25 meters in diameter (about length of classroom) and weighs 235 tons 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

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 World’s largest moveable radio telescope 43 m in diameter & 150 m tall (taller than Statue of Liberty) Original structure collapsed, has been rebuilt

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

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

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

Photo: http://commons. wikimedia

Radio Telescopes Very Long Baseline Array 10 radio telescopes spanning 5,351 miles World’s largest and sharpest (you could be in Los Angeles and clearly read a street sign in New York City 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) Highest array at 16,500’ In Atacama desert, Chile At least 66 telescopes Maximum range = 71,000 square feet of radio light collecting area 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 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): 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: Red has the longest wavelength 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: Far Ultraviolet Explorer (FUSE) – launched in 1999 Galaxy Evolution Explorer (GALEX) – launched in 2003 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: Chandra X-Ray Observatory – launched in 1999 aboard the Columbia. Still in operation Nustar X-Ray Telescope – launched June 13, 2012 to image the sky in high energy x-rays

Chandra

W49b: 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 Photon – packet of electromagnetic radiation (i.e., particle of light) Photons are scarce, takes hours to days to capture one photon Fermi Space Telescope – launched June 11, 2008

Artists illustration of Fermi Space Telescope Photo: http://www.msnbc.msn.com/id/ 26408952/

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

The Sky in Many Wavelengths 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: COBE

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

Milky Way in IR: IRAS Photo: 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 Ultraviolet Photo: http://minho.kasi.re.kr/iCAP/ ImageGallery/0705.AllSky.html

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

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

1st Light for Fermi Gamma Ray Telescope, 8-26-08

Milky Way in Multiple Wavelengths