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									Radio Astronomy


Prepared by Marcia Barton
     and Karen Gram
       July 28, 2006
               Overview

•   Optical Astronomy
•   The Electromagnetic Spectrum
•   Radio Astronomy
•   Project Objective
•   Data from Project
•   Conclusions
                              Optical Astronomy
                                                                        • This optical wavelength
                                                                          picture shows the large
                                                                          spiral galaxy M31 (also
                                                                          known as the Andromeda
                                                                          Galaxy) and its small
                                                                          companions M32, lower
                                                                          center, and M110, to the
                                                                          upper right. Andromeda
                                                                          is the Milky Way’s closest
                                                                          large neighbor at a
                                                                          distance of about 2.2
                                                                          million light-years, and it
                                                                          is very similar in
                                                                          appearance to, and
                                                                          slightly larger than, the
                                                                          Milky Way.
B. Schoening (National Optical Astronomy Observatories) and V. Harvey
(University of Nevada, Las Vegas)
               Pinwheel Galaxy
               (M33, NGC 598)




 M33 in the constellation Triangulum is a prominent
nearby spiral galaxy about 3 million light-years away.
                   Whirlpool Galaxy
                  (M51, NGC 5194/5)




• This showpiece in Ursa Major is likely one of the finest and
  most photographed objects in the night sky.
                    Hydra Cluster of Galaxies
                          (Abell 1060)




• Two nearby
  stars frame
  this cluster of
  galaxies in
  the constel-
  lation Hydra.
                                                              Mars


                       Solar System
         Moon




                                                                     Image courtesy of Nasa
                                              Saturn




REU program, N.A.Sharp/NOAO/AURA/NSF

                                       Voyager 2 Nasa photo
What is an Electromagnetic Wave?


                • Radio waves, television
                  waves, and microwaves
                  are all types of
                  electromagnetic waves.
                  They only differ from
                  each other in wavelength.
                  Wavelength is the
                  distance between one
                  wave crest to the next.
• Waves in the electromagnetic spectrum vary in
  size from very short gamma-rays smaller than
  the size of the nucleus of an atom to very long
  radio waves the size of buildings.
    Move about Wavelengths…
• One way we measure the energy of an electromagnetic
  wave is by measuring its frequency.

• Frequency refers to the number of waves a vibration
  creates during a period of time—like counting how
  frequently cars pass through an intersection.




       Let’s do an activity to show how
        wavelength and frequency are
                    related!
   Wavelength and Frequency
• In general, the higher
  the frequency, or
  number of waves, the
  greater the energy of
  the radiation.

• In other words, the
  shorter the wave, the
  higher the energy.
           Electromagnetic Waves



• The satellite dish connected
  to the television receives the
  signal, in the form of
  electromagnetic waves, that
  is broadcasted from the
  satellites orbiting the Earth.
  The image is displayed on
  your television screen.
               Radio Telescopes




                              Very Large Array (VLA) Radio Telescope in New
                                         Mexico seen from the air

Because the wavelengths of radio light are so large, a radio telescope
  must be physically larger than an optical telescope to be able to
  make images of comparable clarity.
         Can you find your teacher inside
           the VLA Radio Telescope?
                                  Image courtesy of Robyn Harrison




Image courtesy of NRAO/AUI
                Radio Astronomy
                                     NGC 326 – Data from the Very Large
                                     Array Radio Telescope in New Mexico is
                                     the first direct evidence that black holes
                                     actually do coalesce




• Radio waves have the
  longest wavelengths in the
  electromagnetic spectrum.
  These waves can be longer
  than a football field or as
  short as a football.

                                Image courtesy of NRAO/AUI and Inset: STScI
              What is Radio Astronomy?
                                                                     Many astronomical
                                                                       objects emit radio
                                                                       waves, but that fact
                                                                       wasn't discovered
                                                                       until 1932. Since
                                                                       then, astronomers
                                                                       have developed
                                                                       sophisticated
                                                                       systems that allow
                                                                       them to make
                                                                       pictures from the
                                                                       radio waves emitted
                                                                       by astronomical
                                                                       objects.
Image courtesy of NRAO/AUI and A. C. Boley and L. van Zee, Indiana
University; D. Schade and S. Côté, Herzberg Institute for Astrop.
     How can radio waves “see”?
• Objects in space, such as
  planets and comets, giant
  clouds of gas and dust, and
  stars and galaxies, emit light at
  many different wavelengths.
  Some of the light they emit has
  very large wavelengths -
  sometimes as long as a mile!
  These long waves are in the
  radio region of the
  electromagnetic spectrum.

• An optical telescope could not
  see this object in space
  because it would be blocked
  by the giant dust and gas
  clouds. Radio ways can pass
  right through the dust and gas,
  so that an image can be             Image courtesy of NRAO/AUI and David Thilker (JHU),
                                      Robert Braun (ASTRON), WSRT
  formed.
      Why Use Radio Telescopes?
• Radio astronomy can be done      • “Radio telescopes are used to
  during the day as well as the      measure broad-bandwidth
  night.                             continuum radiation as well as
                                     spectroscopic features due to
• Radio astronomy has the            atomic and molecular lines
  advantage that sunlight,           found in the radio spectrum of
  clouds, and rain do not affect     astronomical objects.”
  observations.
                                   • Radio telescopes can detect
• Some celestial objects can not     atoms and molecules that can
  be seen in the visible part of     not be seen with an optical
  the spectrum but do emit radio     telescope. These atoms and
  waves, so they can be imaged.      molecules tell scientists
                                     important information about
                                     how stars and galaxies form.
                      The Milky Way




   Image courtesy of NRAO/AUI


• This composite picture shows the distribution of atomic
  hydrogen in our galaxy.
                     The Milky Way in Different
                           Wavelengths
                                        Seen with radio
                                        waves in the
                                        408 Mhz frequency
Jodrell Bank Mark I and Mark IA, Bonn
100-meter, and Parkes 64-meter




                                                                      NASA/CXC/M.Weiss

                                                                      Seen with the Chandra
                                                                      X-Ray telescope


                                                             Seen in the infrared
                                                               wavelength

                                                            Diffuse Infrared Background Experiment (DIRBE)
     Radio Astronomers Have
 Discovered a Lot About the Milky
              Way!
With radio telescopes,
  astronomers have
  discovered
• The shape and size of
  our galaxy!
• The black hole in the
  center of our galaxy!
• Stars forming and
  dying!
                          Image courtesy of NRAO/AUI and N.E. Kassim, Naval
                          Research Laboratory
Let’s take a closer look at some
astronomical objects in optical,
 radio and other wavelengths!
 Comparison of Solar Energy
Output Variations Over Three
Days in Different Frequencies
     Prepared by Marcia Barton
          and Karen Gram
            July 28, 2006
                     Project Overview
• We used the small radio
  telescope to measure the
  energy output of the sun on
  three separate days at
  approximately the same time
  each day, then compare the
  radio images with optical
  images of the sun at as near
  the same time as we could
  obtain.

• We also look at the raw data
  we obtained from the small
  radio telescope to see if that
  data would give us more
  detailed information than the
  raster map.

                                   Screen shot of the small radio telescope operating software.
Project Overview

    • Using the small radio
      telescope, continuum
      measurements were
      taken in the default
      frequency of 1420
      MHz. A 25-point grid
      scan was used to
      obtain the raster map.
Images of the Sun On July 24, 2006




Raster map imaged by the small radio telescope   SOHO Magnetogram image taken July 24, 2006
    Images of the Sun On July 24, 2006




Raster map imaged by the small radio telescope
                                                     SOHO Extreme Ultraviolet image taken
                                                     July 24, 2006




                                                 Optical wavelength of sun taken July 24, 2006
Images of the Sun On July 25, 2006
      Images of the Sun On July 25, 2006




Srt raster map 7.25.06




                         SOHO Extreme Ultraviolet images 7.25.06
Images of the Sun On July 26, 2006




               Optical sun taken by the National Solar
               Observatory on July 26, 2006
                                           SOHO IMAGES


Srt raster map


                Solar and Heliospheric
    Observatory (SOHO) has an Extreme
    ultraviolet Imaging Telescope (EIT)
    that images the solar atmosphere at
    several wavelengths, and therefore,
    shows solar material at different
    temperatures. In the images taken
    at 304 Angstroms the bright material
    is at 60,000 to 80,000 degrees
    Kelvin. In those taken at 171, at 1
    million degrees. 195 Angstrom
    images correspond to about 1.5
    million Kelvin. 284 Angstrom, to 2
    million degrees. The hotter the
    temperature, the higher you look in    SOHO EIT 284 image taken July 26, 2006
    the solar atmosphere.
Image of the Sun On July 28, 2006




    SOHO EIT 284 image 7.28.06
                Data From the Small Radio
                        Telescope
                        Comparison over 3 days

        60000

        50000

        40000
power




        30000

        20000

        10000

           0
                0   5        10       15         20   25   30
                                     time
          Data From the Small Radio
                  Telescope
                        Rescaled Comparison Data

        20000

        18000

        16000

        14000

        12000
Power




        10000

         8000

         6000

         4000

         2000

            0
                0   5       10         15          20   25   30
                                      time
            Information from SOHO
• Over the past few weeks (date July 21, 2006) this extreme
  ultraviolet observing instrument on SOHO has witnessed at
  least four events where pieces of the Sun have blasted off
  into space. In most instances these are evidence of coronal
  mass ejections, solar eruptions that occur fairly frequently.
  Magnetic tensions above active regions strain and break
  apart, propelling solar particles into space at millions of miles
  per hour.

• The first event on June 26th appears to have been triggered
  by the collapse of a solar prominence suspended by magnetic
  forces above the Sun. While these clouds of particles are
  large, they hardly diminish the bulk of the Sun at all. Don't
  worry: there's plenty left for billions of years to come.
               Conclusions
• The raster map is a contour map of the energy
  output of the sun. Although the raster images
  were similar on different days, closer
  examination of the raw data showed a difference
  of two to three times the magnitude of the
  energy measured.
• This could be a calibration error of the small
  radio telescope. The data was rescaled to
  account for the possible calibration error. When
  the data was rescaled, there was not much
  difference in the radio telescope measurements
  over the three days.
                Conclusions
• When comparing the radio telescope image to
  images made in different wavelengths, UV and
  optical, it is possible that the solar sunspot and
  flares shown on the UV correspond to the
  irregular shape of the raster map.
• However, more extensive data collection would
  be needed to obtain baseline data for the sun
  and insure accurate calibration of the small radio
  telescope.
                        References
National Radio Astronomy Observatory. August 6, 2004.
  http://www.nrao.edu/whatisra/FAQ.shtml. July 26, 2006

Sky and Telescope. www.skyandtelescope.com. July 24, 2006.

Hubble. http://hubblesite.org/ July 27, 2006.

Nasa Astronomical Data Center. http://adc.gsfc.nasa.gov/ July 25, 2006

National Optical Astronomy Observatories.

National Solar Observatory. http://www.nso.edu/ July 27, 2006.

SOHO. Solar and Heliospheric Observatory. July 28, 2006.
  http://sohowww.nascom.nasa.gov/ downloaded July 24-27, 2006.
          References

And of course…..

  Thank you Lisa Young and
  Robyn Harrison for all your
  kind and informative help!

								
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