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  • 1

    The Electromagnetic The Electromagnetic SpectrumSpectrum

    Can you see me now?Can you see me now?

    EE--M RadiationM Radiation

    Each wavelength of electro-magnetic radiation (light) brings us unique information.

    Almost everything we know about the Universe comes from the study of the electromagnetic radiation emitted or reflected by objects in space.

    Objects in space send out electromagnetic radiation at all wavelengths - from gamma rays to radio waves.

    The electromagnetic spectrum can be expressed in different terms, or units:

    Energy is measured in electron volts (eV).

    Frequency is measured in cycles per second (Hertz or Hz or kHz),

    Wavelength is measured in meters (m) or nanometers (nm).

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    Radio WavesRadio WavesHave the longest wavelengths. Have the longest wavelengths.

    These waves can be as long as a These waves can be as long as a mile. mile.

    These are the same waves that These are the same waves that carry signals for your television carry signals for your television and cellular phones. and cellular phones.

    How do we "see" using Radio How do we "see" using Radio Waves?Waves?

    Radio telescopesRadio telescopes::dishes dishes made out of a conducting metal made out of a conducting metal reflect radio waves to a focus point. reflect radio waves to a focus point. are much, much larger than an optical are much, much larger than an optical telescope.telescope.are often combined into an array. are often combined into an array. often act together as one large telescope. often act together as one large telescope.

    The Very Large Array (VLA), in New Mexico.

    27, 81 ft diameter, radio telescopes work together.

    The Arecibo site in Puerto Rico is embedded in limestone in the jungle.

    The dish is over 1000 ft wide and uses the rotation of the Earth to examine space.

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    The Sun in radio waves How do we "see" using How do we "see" using Microwaves?Microwaves?

    Cosmic Background Explorer (COBE)

    The Wilkinson Microwave Anisotropy Probe (WMAP)

    Microwaves in SpaceMicrowaves in Space

    This Cosmic Background Explorer (COBE) image is of the cosmic microwave background of the

    visible universe. The pink and blue colors show tiny fluctuations.

    If you had a very sensitive microwave telescope in your house you could detect faint signals coming from all directions.

    This is the Cosmic Microwave Background!

    The Sun in Microwave

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    InfraredInfrared

    Two categories:Two categories: Far infrared" waves are thermal Far infrared" waves are thermal

    and are closer to the microwave and are closer to the microwave region of the electromagnetic region of the electromagnetic spectrum.spectrum.

    "Near infrared" wavelengths are "Near infrared" wavelengths are closer to visible light and are not closer to visible light and are not hot at all.hot at all.

    Infrared light is between visible light and microwave.

    The Sun in Infrared Light

    The Orion constellation as seen in visible light and IR.

    (Photos courtesy of JPLs Herschel Space Observatory Website)

    Visible Light WavesVisible Light Waves

    ROY G BIV

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    Ca-K light (filtered)

    White light(unfiltered)

    The Sun in Visible Light Ultraviolet WavesUltraviolet Waves

    UV is divided into three regions: UV is divided into three regions:

    near ultravioletnear ultraviolet far ultraviolet, and far ultraviolet, and extreme ultravioletextreme ultraviolet

    Ultraviolet (UV) light waves are shorter visible li ght. Ultraviolet (UV) light waves are shorter visible li ght.

    Three galaxies images in both visible and ultraviolet light.

    NASA's Ultraviolet Imaging Telescope.

    The Sun in Extreme Ultraviolet Light

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    Sun in UV radiation. Sun in extreme UV.

    XX--raysrays

    Earth's atmosphere is so thick XEarth's atmosphere is so thick X --rays rays cannot penetrate it. cannot penetrate it. XX--ray telescopes are mounted on ray telescopes are mounted on satellites in space.satellites in space.They are used to view high energy They are used to view high energy substances like black holes, supernovas, substances like black holes, supernovas, and more. and more.

    This is a photo of the Sun's X-ray radiation.

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    The Sun in X-Rays GammaGamma --raysrays

    Gamma-rays are the most energetic.

    They are produced by the hottest regions of the universe.

    The high-energy gamma photons pass right through normal telescope devices.

    Gamma-ray telescopes map the energy path when a gamma-ray strikes an electron and loses energy.

    A computer processed image of the Crab Nebula in the "light" of gamma-rays.

    The Crab nebula was created by a supernova that brightened the night sky in 1054 A.D.

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    Sun in Gamma

    RadioRadioFarFar--InfraredInfraredMidMid--InfraredInfraredNearNear--InfraredInfrared

    Visible: ColorVisible: ColorVLTVLT

    Visible: DSSVisible: DSSUltravioletUltravioletXX--RayRay

    Why Do We Have to Go to Space to See All of the Electromagnetic Spectrum?

    Atmospheric interference!

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