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Extra-Galactic Hydrogen Line Observations

A System for Observing Neutral Hydrogen Line Emissions in Nearby Galaxies


The observation of neutral hydrogen (HI) line emissions from within our home galaxy (the 'Milky Way') is a medium level difficulty project for the amateur radio astronomer. The detection of HI line emissions outside our galaxy presents an additional level of difficulty.

The project described here is designed to determine whether extra-galactic neutral hydrogen (HI) line emissions from nearby galaxies can be detected using a small 3 metre diameter TVRO-style mesh dish.

In years gone past detection of any hydrogen line emissions were out of reach of the amateur as a quote from one of the author's reference books states (circa 1975)...

"Unfortunately for amateurs, this 21 cm equipment is either too elaborate or too expensive for the average household budget.  Until microwave equipment becomes available at a much lower cost, there is little point in pursuing the idea any further"

Fortunately for today's amateur radio astronomer, that time has well and truly arrived.


It could be argued that HI observations are second only to the detection of pulsars in terms of difficulty for the amateur radio astronomer with 'backyard level' systems.

The detection of extra-galactic neutral hydrogen is, in general, a significantly harder task than detecting neutral hydrogen line within our own galaxy - and thus provides an interesting challenge.

The galaxy targets for detecting extra-galactic neutral hydrogen line signals in this project, initially, are two external galaxies - the Magellanic Clouds - comprised of the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC).

Check the 'Results' tab to see details of the observations conducted at NRARAO so far...

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