The Electromagnetic Spectrum

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The Electromagnetic Spectrum

• A Very Short Discussion of Waves.

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Waves

• Waves are pure energy.
• Waves carry energy from place to place.
• Examples of waves are
• Heat
• Sound
• Light
• Water

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Characteristics of Waves

• All waves have
• Wavelength ( l )
• Amplitude
• Speed how fast a crest travels from one place
  to another.
• Frequency how many waves pass a point in a unit
  of time.

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Electromagnetic Waves

• The E-M spectrum contains waves that have similar
  characteristics.
• These waves do not require a medium and travel at
  the speed of light. 186,000 miles per hour

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The Electromagnetic Spectrum
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How is the Electromagnetic Spectrum used in
astronomy?
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Radio Waves

• Have the largest wavelengths of all light waves.
  They can be up to several kilometers long.
• Used in Radios, TVs, Communication, and cell
  phones.

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Radio Waves and Astronomy

• Space objects emit light at many different
  wavelengths.
• Some of the wavelengths are in the radio wave
  area of the EM spectrum.
• Radio waves are collected by radio telescopes and
  intrepreted.

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Radio Telescopes
Very Large Array (VLA)

• Parks Radio telescope

These radio telescopes reflect radio waves into a
single focal point where they are collected.
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What do radio waves show us?

• Different astronomical objects emit different
  lengths of radio waves.
• Scientists can study these emissions in order to
  learn about the makeup and structure of the
  universe.

CO gases in our milky way galaxy as seen by radio
waves
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Microwaves

• Have wavelengths that can be measured in
  centimeters
• Used in communication, cooking food, sensing, and
  imaging.

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RADAR

• An acronym for radio detection and ranging
• Developed to determine an objects position by
  firing bursts of microwaves and recording their
  echo.
• Microwaves are able to penetrate haze, clouds,
  and snow.

A radar image from the Space Shuttle.
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Cosmic Microwave Background

• The universe is constantly giving off microwaves.
  This phenomenon has been dubbed Cosmic Microwave
  background.

Cosmic Background Explorer (COBE) image
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Infrared Radiation

• Ranges in size from a single cell to the head of
  a pin.
• Used in imaging, heating food, and remote
  controls.
• Long infrared rays cab be felt as heat, short
  ones cannot be detected by humans.

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How do we see with infrared?

• Any object that has a temperature radiates
  infrared radiation (much in the same way very hot
  objects will emit visible light)

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Making Infrared Pictures

• A special camera is used that is able to detect
  temperature. Each temperature is assigned a
  different false color. Generally, the warmer
  an object, the more red or orange it is. The
  colder, the more blue. This is an image of a cat
  in infrared.

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So why use it in Astronomy?

• It is easy to study cloud structure. Dark clouds
  are warmer than light clouds.
• We are able to study the effects of urbanization
  on the earth.

What do the red areas represent in this satellite
image?
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• Infrared images can tell us things about space
  such as the concentration of stars and dust.

Image of the Milky Way. The hazy, horizontal
S-shaped feature that crosses the image is faint
heat emitted by dust in the plane of the Solar
System
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Visible Light

• The only electromagnetic waves we can see.
• Their intensities range from red to violet with
  violet being the highest in energy.

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True Color vs False Color

• True coloran image that is the same as our eyes
  would see it.
• False colorcomputers record numbers relating to
  brightness in another area of the spectrum such
  as radio waves. The computer then assigns values
  to these intensities. It is much like color by
  number!

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True Color image of Phoenix, AZ
False Color image of Phoenix, AZ
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The planet Uranus in False and true color.
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Ultra Violet Radiation

• Used in tanning booths, sterilization
• Responsible for sun burns and eye cataracts

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Ultra Violet Light and Astronomy

• Hubble Space telescope uses UV light

Satellite image of the sun in ultra violet light.
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The hottest and most active objects in the
universe give off UV light. Scientists can learn
about these objects by studying the amount of UV
light given off.
False color image of the earth using UV light.
Which side of the Earth is facing the sun? How
do you know?
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• Pictures like the one above show which galaxies
  are new and which ones are old. The top row
  shows three galaxies in UV light and in visible
  light in the bottom.

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X-Rays

• Used in x-ray photographs.
• Extremely small wavelength. Extremely high
  frequency and energy.
• The earths atmosphere is thick enough that
  x-rays are not able to penetrate to the surface.

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• When the Sun shines on us at a certain angle, our
  shadow is projected onto the ground. Similarly,
  when X-ray light shines on us, it goes through
  our skin, but allows shadows of our bones to be
  projected onto and captured by film.

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X-Rays in Astronomy

• Astronomers are able to load x-ray detection
  machines on to satellites.
• These satellites are able to detect things like
  the number of photons collected, the energy of
  the photons collected, or how fast the photons
  are detected, can tell us things about the object
  that is emitting them.

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• Many things in space emit X-rays, among them are
  black holes, neutron stars, binary star systems,
  supernova remnants, stars, the Sun, and even some
  comets!

http//chandra.harvard.edu/
The sun in x-ray
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Gamma Rays

• Have the smallest wavelength, highest frequency,
  and highest energy of any other type of
  electromagnetic radiation.
• Generated by radioactive atoms in nuclear
  explosions.
• Produced in the hottest regions of the universe
• Things like supernova explosions (the way massive
  stars die), neutron stars and pulsars, and black
  holes are all sources of celestial gamma-rays.

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Gamma rays give us information into such things
as nebulas.