Radio Astronomy

1
Radio Astronomy

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

2
Overview

• Optical Astronomy
• The Electromagnetic Spectrum
• Radio Astronomy
• Project Objective
• Data from Project
• Conclusions

3
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 Ways 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)
4
Pinwheel Galaxy(M33, NGC 598)

• M33 in the constellation Triangulum is a
  prominent nearby spiral galaxy about 3 million
  light-years away.

5
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.

6
Hydra Cluster of Galaxies (Abell 1060)

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

7
Solar System
Mars
Moon
Image courtesy of Nasa
Saturn
REU program, N.A.Sharp/NOAO/AURA/NSF
Voyager 2 Nasa photo
8
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.

9

• 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.

10
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 timelike
  counting how frequently cars pass through an
  intersection.

Lets do an activity to show how wavelength and
frequency are related!
11
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.

12
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.

13
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.

14
Can you find your teacher inside the VLA Radio
Telescope?
Image courtesy of Robyn Harrison
Image courtesy of NRAO/AUI
15
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
16
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.
17
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
  formed.

Image courtesy of NRAO/AUI and David Thilker
(JHU), Robert Braun (ASTRON), WSRT
18
Why Use Radio Telescopes?

• Radio astronomy can be done during the day as
  well as the night.
• Radio astronomy has the advantage that sunlight,
  clouds, and rain do not affect observations.
• Some celestial objects can not be seen in the
  visible part of the spectrum but do emit radio
  waves, so they can be imaged.

• Radio telescopes are used to measure
  broad-bandwidth continuum radiation as well as
  spectroscopic features due to atomic and
  molecular lines found in the radio spectrum of
  astronomical objects.
• Radio telescopes can detect atoms and molecules
  that can not be seen with an optical telescope.
  These atoms and molecules tell scientists
  important information about how stars and
  galaxies form.

19
The Milky Way
Image courtesy of NRAO/AUI

• This composite picture shows the distribution of
  atomic hydrogen in our galaxy.

20
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)
21
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
22
Lets take a closer look at some astronomical
objects in optical, radio and other wavelengths!
23
Comparison of Solar Energy Output Variations Over
Three Days in Different Frequencies

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

24
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.
25
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.

26
Images of the Sun On July 24, 2006
SOHO Magnetogram image taken July 24, 2006
Raster map imaged by the small radio telescope
27
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
28
Images of the Sun On July 25, 2006
29
Images of the Sun On July 25, 2006
Srt raster map 7.25.06
SOHO Extreme Ultraviolet images 7.25.06
30
Images of the Sun On July 26, 2006
Optical sun taken by the National Solar
Observatory on July 26, 2006
31
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 the solar atmosphere.
SOHO EIT 284 image taken July 26, 2006
32
Image of the Sun On July 28, 2006
SOHO EIT 284 image 7.28.06
33
Data From the Small Radio Telescope
34
Data From the Small Radio Telescope
35
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.

36
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.

37
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.

38
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.nas
  a.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.

39
References

• And of course..

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