DIY Radio Telescope tracks the Milky Way #Astronomy @IEEESpectrum

IEEE Spectrum writes about detecting galactic hydrogen using roof flashing, a paint-thinner can, and a software-defined radio

Davis Schneider writes:

How big a radio antenna would you need to observe anything interesting? It turns out the answer is a half meter across. For less than US$150 I built one that size, and it can easily detect the motions of the spiral arms of the Milky Way galaxy. Wow!

The hardest part is getting the materials right and the correct positioning of the short antenna within the larger one. Online tutorials and calculators help. And the results are quite good:

Spiral Arms: The antenna can detect emissions from the hydrogen gas in nearby arms of the galaxy: Dark green [above] represents the signal from the sky; light green shows the baseline system response with no signal.

This plot distinctly showed a hydrogen “line” (really a fat bump) when I pointed my horn at the star Deneb, which is a convenient guide star in the constellation of Cygnus. Point at Cygnus and you’ll receive a strong signal from the local arm of the Milky Way very near the expected 1420.4-MHz frequency. Point it toward Cassiopeia, at a higher galactic longitude, and you’ll see the hydrogen-line signal shift to 1420.5 MHz—a subtle Doppler shift indicating that the material giving off these radio waves is speeding toward us in a relative sense. With some hunting, you may be able to discern two or more distinct signals at different frequencies coming from different spiral arms of the Milky Way.

Read details in the entire article here.

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