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.
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| 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.
