Radio Astronomy Listening to the Sky

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Slide 1

Radio Astronomy Listening to the Sky

Jeremy P. Carlo

N2ZLQ

Renfrew County Amateur Radio Club

January 17, 2011

Slide 2

The electromagnetic spectrum

Theory: Maxwell (1860s):

Light as special case of EM

Slide 3

The electromagnetic spectrum

EM radiation

characterized by

wavelength l

frequency f

energy E

& constant speed c

Ranges:

Radio

Microwave

Infrared

Visible

Ultraviolet

X-rays

Gamma rays

Slide 4

The electromagnetic spectrum

Infrared: late 1700’s/early 1800’s

X-rays: Roentgen – cathode rays

Gamma: Curies et al. – radioactivity

Radio: experiments start with Hertz (1880s)

Transmission/reception of radio waves

Then Marconi, Tesla, etc.

What about using radio waves for astronomy?

Slide 5

Production of Radio Waves

(terrestrial) currents in wires

Crossed E, B, fields…

Atomic resonances

Low-energy electronic transitions

Rotational/vibrational modes

Magnetic (e.g. hyperfine) interactions

Synchrotron radiation

Acceleration of charged particles

Strong B fields, high energies!

Or, other types of EM radiation that have been Doppler shifted…

Slide 6

EM Radiation in Astronomy

Only some EM radiation gets through the earth’s atmosphere.

“Window” for visible light (some IR also)

Another window in radio!

Pretty much everything else requires satellites (a little can be done with high-altitude balloons)

Slide 7

EM Radiation in Astronomy

Up until ~1900 only visible light astronomy was done!

But there’s so much more to “see!”

Slide 8

The Birth of Radio Astronomy

First astronomical radio observation

Karl Jansky, 1932-1933 (Bell Labs)

Investigate sources of radio noise

Steerable phased array at 20.5 MHz

Lots due to thunderstorms

Found signal that repeats every day (not exactly… 23h 56m)

Now identified with galactic center

(supermassive black hole!)

Karl Jansky, 1905-1950

Slide 9

The Birth of Radio Astronomy

Bell Labs was satisfied with Jansky’s identification of QRN sources… no more studies needed!