June 20, 2008

In Today's One Minute Astronomer...

The Mysterious "Hiss" From The Milky Way (Part 2)

Four years after Karl Jansky's discovery of radio waves from the Milky Way, a young radio engineer named Grote Reber built the world's first radio telescope... by himself… in his backyard!

The Basics

• Reber was a ham radio operator, studied radio engineering, and worked for several radio manufacturers in Chicago from 1933 to 1947.

• Reber learned of Jansky's discovery of "cosmic radio waves" in the newspapers. He applied to work with Jansky at Bell Labs in Holdmel, New Jersey. But the Great Depression prevented Bell from hiring new staff.

• He was completely captivated by Jansky's cosmic radio waves, so Reber built what became the world's first radio telescope at his own expense while working full time as a radio engineer.

• He made the reflector from sheet metal 30 feet in diameter. Just like an optical telescope, Reber's construction used a parabolic mirror to focus all wavelengths to a single point. There, 20 feet above the dish, he mounted his radio receiver to amplify the faint cosmic signals by million of times, making them strong enough to record on a strip chart.

Grote Reber's Backyard Radio Telescope... And The World's First

A Deeper Look

• From his backyard radio telescope, Reber confirmed Jansky's discovery of radio waves from the Milky Way, and found radio emission from the sun, and mysterious radio sources in Cassiopeia and Cygnus.

• From 1938 to 1943, Reber made the first surveys of radio waves from the sky and published his results widely. His work ensured radio astronomy became a major field of research following World War II.

• When other researchers began covering more and more of the spectrum, Reber turned to longer-wavelength radio waves in the 1950's. Such signals penetrate the Earth's atmosphere in only a few places, one of which is Tasmania. Reber spent his last years there, and died in 2002 at the age of 90.

Good To Know

The radio waves Jansky and Reber detected from the disk of the Milky Way came from electrically charged particles blasted into interstellar space by supernova explosions.

Personal View

Reber's work was the end of golden age of astronomy, when an accomplished amateur could make groundbreaking discoveries. This often happens in a new and young science, where professionals, by definition, don't yet exist.

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