October 22, 2011 - Happy Birthday, Karl Jansky

Have you ever seen those big radio telescopes, which look like big dishes pointing up at the sky? What are they listening to? Who in outer space is sending radio waves to Earth?

Not so much who, as what!

Let's find out how radio astronomy got started in on honor of one of its founders, Karl Jansky (born on this day in 1905, in the Territory of Oklahoma).

Jansky studied physics, and he went to work for Bell Telephone Laboratories, where he investigated the atmosphere and how it affects radio and telephone transmissions. in other words, he was studying what makes radio static. 

This is a replica of Jansky's
radio telescope.

He built a large antenna – about 100 feet wide and 20 feet tall – and he mounted it on a turntable so he could point it in any direction. This huge antenna was sometimes called “Jansky's merry-go-round.” He listened to static, and he categorized the sorts of static he heard into several groups. One was nearby thunderstorms, one was far-away thunderstorms, and the last... The last was a puzzle.

And puzzles are very interesting to scientists!

Jansky spent over a year investigating the sources of a faint, steady hiss of static. The intensity of the hiss rose and fell once a day, so Jansky wondered if it could be coming from the Sun. But after a few months, the most intense point of the static moved away from the sun. Jansky finally realized that the hiss seemed to coming from the center of our galaxy – the center of the Milky Way.

Jansky published his findings and got a lot of attention for his paper. However, Bell Laboratories wouldn't fund Jansky following up with a larger antenna—they reassigned him to another project—and so it was up to other scientists to develop radio astronomy further.

How does radio astronomy work, exactly?

Radio waves are a kind of electromagnetic radiation, like X-rays, the microwaves in our microwave oven, and visible light. Radio waves have the longest wavelengths of these.

Stars, galaxies, black holes, supernovas and even the Big Bang can all be studied from the radio waves they emit (or emitted). An “active” planet like Jupiter, which has violent super-storms in the various layers of its atmosphere, emits radio waves, and of course our Sun emits radio waves as well.

Here's a great source to learn about radio astronomy.