Wednesday, April, 27, 2011

Radio Astronomy

Troy RussellB-Section Physics Club Treasurer

EE MajorAcoustics Minor

Topics

• What• When• How• Who• Where• Why• Project• Sources

What

• Cosmic Microwave Background Radiation• Cold Space image• View Hydrogen Motion• Black Hole study

This composite image of the Whirlpool Galaxy, Messier 51, shows that the radio emission from the galaxy’s cold hydrogen gas (blue) extends well beyond the optical light emitted by its stars (Credit: NRAO/AUI, J. Uson).

When

• 1930’s• Bell Labs• Karl Jansky

o Radio Telecommunications Experimentationo Static Interference with Signalo First thought was from Suno Repeated every 23 hours 56 minutes (Sidereal Day)o Milky Way Galaxy

How

• Singular Sky Scan• EM waves• Dish

o Reflector• Receiver

o Dipole Antenna• Interferometry

Reflector

• Large Dish• Four Configurations

o Axial Feedo Off-Axis Feedo Cassegraino Gregorian

• Parabolic Shape• Focus EM radiation• Imperfections: <λ/20

Reflector Configurations

Dipole Antenna

• An antenna is a device for converting electromagnetic radiation in space into electrical currents in conductors or vice-versa, depending on whether it is being used for receiving or for transmitting, respectively

Perpendicular Dipole

• End of Waveguide• Collect Radiation from

other Polarized patternso Linearo Circularo Elliptical

Low Noise Block Down ConverterUsing a Perpendicular Dipole Antenna

Interferometry

• Signal A received• Signal B received

later• Time based signals

overlaid with delay removed

• Signal A + Signal B = Greater Resolution

Who

• Astronomers• Scientists• Researchers

Where

• Anywhere / Anytimeo Radio pierces cloud covero Day or Nighto Some interference from local radio frequency

based systems on ground or orbit

Why

• Cosmic Rays• Study Earliest Generation of a Galaxy• Big Bang Knowledge• Black Holes• Neutral Hydrogen• Pulsars• Cold Gas

The Rotating Disk of M33

Project

• Itty Bitty Radio Telescopeo Stage 1: Acquire partso Stage 2: Assemble Telescopeo Stage 3: Begin Simple Testingo Stage 4: Add Refinements

Acquire Parts

• Craigslisto Dish

• Radio Shacko Cables/Hardware

• Est. Price ~ $30-$40 (Pending Conditions)• Time Spent Acquiring Parts:

o 3 – 6 Hours

Assemble Telescope

• Simplistic Design• Easy Directions• Total Time Spent in Assembly:

o 2-4 hours

Simple Testing

• Point Telescopeo Suno Moono Radio Transmitterso Etc.

• Gain Understandingo Sourceso Scope Usage

• Time Spent Testing:o 2 – 6 Hours

Add Refinements

• Attach Scope to PC• Create Images on PC• Sensitivity• Plan second iteration

o More Complexo Interferometryo Larger Disho Endless Possibilities

• Time Adding Refinements:o 2 – 10 Hours

Benefits

• Team building• Club equipment construction• Radio Telescope

o Conceptso Usage methodso Potential Researcho Future refinement projectso Future Astronomy Projectso Possible Outreach

Sources

• Gay, Pamela L. "Astronomy Cast Episode 130: Radio Astronomy." Interview by Fraser Cain. Audio blog post. Astronomy Cast. Web. 7 Apr. 2011. <http://www.astronomycast.com/astronomy/episode-130- radio-astronomy/>.

• "Radio Astronomy." National Radio Astronomy Observatory (NRAO): Look Deeper. NRAO. Web. 07 Apr. 2011. http://www.nrao.edu/index.php/learn/radioastronomy

• Basics of Radio Astronomy for the Goldstone-Apple Valley Radio Telescope - Diane Fisher Mille

• http://www.lesia.obspm.fr/plasma/Goutelas2007/Presentations/Torchinsky/Torchinsky-History.pdf

• National Science Foundation Website• Kutner, Marc. "4.8 Radio Astronomy." Astronomy: A Physical Perspective.

Cambridge UP. 69. Print.