Radio Astronomy – An Unseen Field

(Last Updated On: August 6, 2019)

Ahh… Technology, from rockets in NASA to the android phones we operate. It helps like a good old pal. Little do we know that these operate on the sector of electromagnetic waves which gives a very spectacular yet a new look into our universe. Excited to know? Right? So let’s get started.

The Radio

Since long-time humankind knew about the electromagnetic spectrum and the existence of radio waves in it, thanks to James Maxwell and Rudolf hertz. It was also established that sources from outer too can create radio signals but no one was able to detect them. But in 1895 Marconi proved that we can also harness the electromagnetic spectrum to use this part of the spectrum for our communication and industrial needs. And after that, we never went back, from large radio stations to now Bluetooth and remote devices, all thanks to radio transmission. But we are getting ahead of ourselves, for now, let’s return to our first long-range signal by Marconi.

radio astronomy
Guglielmo Marconi (1874 – 1937)

After Marconi’s extraordinary feat radio was being used in large companies as a means to communicate important messages across continents. Many industries actually provided such services of providing these lines of communication via radio. One such was Bell labs which provided its client a Trans Atlantic Communication using powerful shortwave transmitter. But Scientists and engineers working for the communications companies noticed that, at various times during the year, excessive amounts of static interference interfered with communications. Bell laboratories assigned Jansky to investigate the possible sources of this periodic interference phenomenon. As a radio engineer, Jansky was assigned the job of investigating sources of static that might interfere with radio voice transmissions.

Thus for his investigation, he built the world’s first-ever radio telescope. It was an antenna designed to receive radio waves at a frequency of 20.5 MHz (wavelength of about 14.6 meters). It was mounted on a turntable that allowed it to be rotated in any direction. Fun fact as it was capable of turning it was called janskys merry go round. Well then he collected radio data for months and classified them into three categories which were nearby and distant thunderstorms while the third category was called and I quote “a faint steady hiss of unknown origin”. The origin of the disturbance was located in the Sagittarius constellation (which happens to be the direction of the center of our galaxy). This discovery was then published in the New York Times in 1933.

And Then

In 1935 he wanted to investigate more about the source in the Sagittarius constellation but he found little support from either astronomers, for whom it was completely foreign or Bell Labs. Also, the recession also discouraged any research institution to take research that risky at that time.  The world wars made this field dormant for a long time but not for long my friends.

After the great wars, someone named Grote Reber was astounded about Jansky’s research. So to pursue this as his field of work and applied for a job in bells labs where Jansky was working, but couldn’t get it due to the great depression. But sticking to the will of pursuing this field he constructed a radio telescope of his own in his backyard in the summer of 1937. It was even more powerful than the one made by Jansky. It was a metal parabolic dish of 9 meters diameter with a receiver 6 meters ahead of it in the foci of the parabola.

Then in September of the same year, he started taking observations from the telescope but unlike Jansky, he systematically studied the sky in parts. Through his study, he started publishing many research works in the new field of “radio astronomy”. Then in 1941, he started to make radiofrequency sky map which he extended till 1943. And after the Second World War, there was a literal boom in research in this field as many scientists returned from the war effort. Engineers and scientists started building bigger and more sophisticated telescopes. And after that the rest was history.

The Present

Gone were the days when telescopes made by Reber were called sophisticated, nowadays telescopes are made with ALMA, VLA, ARECIBO, GREEN BANK TELESCOPE and finally the pride of nation India that is the Giant Meter Wave Radio Telescope or GMRT in short spanning with dish receivers meters in size and spread in kilometers in area to receive even the faintest signal from the cosmos.

Radio Astronomy
GMRT, Maharashtra, India

The Bigger, The Better. But Why?

Now you might be thinking why to build such large and bulky instruments. Well, my friends, I give you two words: resolution and sensitivity.

Basically, any instrument in science is solely made for one purpose that is to give accurate and precise results. That’s why you see so many people working on a project like LIGO which is basically an interferometer. But it is made so sensitive that it can sense waves even millions of light-years away with amplitude lesser than the thickness of our hair.

I digress, so resolution means how much clearer can you see or more precisely how much close two objects should be to not be distinguished by the said receiver. On the other hand, sensitivity tells us how much fainter or in our case low-frequency objects can you detect. In the case of visual astronomy it is just a matter of few hundred meters as the wavelength   itself ranges in nanometres, but in case of radio signals they lie from a few millimeters to meters in wavelength thus to even achieve a sensitivity that we achieve by our normal telescopes used by us a receiver of near kilometers is to be made which is very costly as a project. So scientist uses aperture synthesis to create an apparent sized telescope at a cheaper price.

Future

Seeing the current progress one might think that we have reached the epitome of this field where we can receive any radio signal sent to us from outer space. But fortunately, we are far away from that stage. We lack to use the potential of using space-based radio telescope as of now even the biggest feat of capturing the image of black hole Sagittarius A* took us nearly two years of data and coordination of radio telescope from all over the world to capture it. But still, the future looks bright as we now prepare ourselves construct the largest ever radio telescope which is called  The Square Kilometre Array or SKA. And the even better news is that India is also a leading contributor to this effort. Indian engineers and scientists from NCRA are helping to design this telescope to be as cheap as possible. This project will be conducted on two places which are Australia (SKA south) and Chile (SKA mid) spanning over an apparent capture of a square kilometer.

The Square Kilometre Array
The Square Kilometre Array – Radio Telescope

So this is it for today, hope you enjoyed learning about this new field in astronomy and would be curious to know more. But until then see you next time, and be curious.

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