Illustration of Radio astronomy

1933 Radio astronomy

The book of science

Tom Sharp

Karl Guthe Jansky astronomy Illustration of Radio astronomy

Radio astronomy

Stars, galaxies, quasars, pulsars, and masers emit radio waves, and once we didn’t know it. Our instruments were too primitive to detect them. We thought the earth’s ionosphere was blocking them. Until Karl Guthe Jansky, investigating the source of static that interfered with shortwave receptions, discovered a signal repeating every sidereal day that wasn’t coming from the sun. It came from the mysterious heart of our galaxy in the constellation of Sagittarius.

Sagittarius A*

At the center of the Milky Way, hidden by clouds of cosmic dust, stars and ions orbit a massive black hole. We cannot see the thing itself, heavy as four million solar masses, only emissions from things that orbit it.


To conduct radio astronomy, unlike radar or normal radio, we don’t send the signals. The universe is full of things, wacky and violent, sending signals on their own. It’s just an accident of physics. The universe isn’t trying to talk to us.

Radio astronomy is consistent with the adage that you can learn a lot if you only learn to listen. Karl Guthe Jansky’s and later discoveries in radio astronomy became possible only as our technology improved.

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