Noisy Skies

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[audio: radio hiss, static, crackle; "˜squeal' of tuning a shortwave radio]

The Milky Way climbs the eastern sky after midnight on May nights. It's the combined glow of millions of stars in the disk of our home galaxy.

The Milky Way glows in just about every form of energy, from radio waves to X-rays. In fact, the discovery of radio waves from the Milky Way made headlines 75 years ago this month.

Bell Labs had assigned a young engineer named Karl Jansky to check out sources of static on the radio waves used for long-distance radio transmissions. Jansky built a receiver on a platform that could be turned to track the direction of radio signals.

Jansky found that most of the static came from thunderstorms. But there was a "œhiss" that he couldn't explain. It peaked once a day, so he first thought it came from the Sun.

After tracking it for a few months, though, Jansky found that the signal peaked about four minutes earlier each day. Since the distant stars rise and set four minutes earlier each day, Jansky concluded that the static came from the stars. The strongest signal came from the Milky Way -- and particularly from the constellation Sagittarius, which is home to the galaxy's heart.

With the problem solved, Jansky turned to other work, and never went back to studying the stars. Even so, he's considered the father of the field of radio astronomy. [more radio static]

Script by Damond Benningfield, Copyright 2008

For more skywatching tips, astronomy news, and much more, read StarDate magazine.