Observatory Builds Radio Telescope To Probe Structure of Galaxy

Harvard astronomers this fall opened a new era of stellar exploration in America.

In an effort to bring the United States up to date on similar work which began recently in the Netherlands and Australia, Provost Buck announced this week:

1) The immediate launching of a research program in radio astronomy with an initial two-year outlay of $32,000 from the National Science Foundation and an anonymous gift believed to be of comparable size.

2) Construction of a giant radio telescope and related electronic apparatus at the Observatory's Agassiz station in Harvard, Massachusetts.

Bart J. Bok, Robert W. Wilson Professor of Applied Astronomy, and Harold I. Ewen, Research Associate at the Observatory, are in charge of the projects.

Bok said yesterday that work is "already past the bulldozer stage." Building of the telescope house is proceeding rapidly at Agassiz Station. Ewen"s own firm is finishing the telescope's electronic receiver, while a Cohasset radar company has completed the tubular aluminum antenna (above).

Helicopter Aid

Transporting the 25 foot, 800-pound parabolic antenna frame the 50 miles from Cohasset to Harvard is a problem, Bok admits. However, an Air Force helicopter may be used within the next ten days to do the job.

The radio telescope may give astronomers greater insight into the structure of the universe, particularly of our galaxy--the Milky Way--which scientists believe to have a pinwheel shape with the sun in the middle and spiral arms of stars and gasses circling out from this center.

After sufficient research with the new telescope, Bok says astronomers will be able to chart reasonably well these spiral arms and eventually fit the earth in its proper position on or near one of them.

There are three ways of showing the spiral shape of our galaxy: 1) By tracing the gaseous emissions of blue-white "super giant" stars (10,000 time as bright as the sun) 2) By tracing clouds of hydrogen gasses that tend to follow the spiral arms and 3) By tracing cosmic dust.

The Agassiz telescope will further explore the second method. Formerly, telescopes could pick out only ionized hydrogen which recombined with free electrons and radiated light in the visible spectrum.

The new apparatus, however, can record the energy released by invisible radiation from the neutral hydrogen atom when its single electron does a "flip flop" (reverses its spin). By calculations astronomers can then place the gaseous clouds in their proper position in space.

Using an equatorial mount (one of the axes parallel to the polar axis of the earth), the Agassiz radio telescope may be focused on a special spot in the sky for long periods of time, simply by compensating for the earth's rotation.

In addition to tracing hydrogen clouds, the telescope will search for new spectrum lines, especially that of the element deuterium ("heavy hygrogen") and radiation from other galaxies and from the sun.

Ironically it was the Physics department here that developed a radio telescope; this is the astronomy department's first research project in the field.

Ph.D. Incentive

In 1950, Nobel Prize winner Edward M. Purcell, professor of Physics, gave Ph.D. candidate Ewen the research project idea that there might be measurable radiations from the atomic particles of hydrogen floating in the Milky Way.

Ewen took the challenge and built up antenna and associated detection equipment. Twice his electronic apparatus proved too insensitive; but the third model (pictured above) worked on the first try.

In March 1951, Purcell and Ewen announced that these hydrogen clouds radiate at a wavelength of 21 centimenters, and Ewen got his Ph.D. in Physics. The latter still insists, "Purcell provided the brains, I just the brawn."

While teaching here in 1951, Dutch astrophysicist H. C. van de Hulst gathered some information and equipment from Ewen and transmitted them to Leiden University astronomers. Work done at Kootwijk with slightly different equipment verified Ewen's report, which was further confirmed by the findings of an Australian radio telescope

The Agassiz telescope will still not be the world's largest; the Dutch are erecting a 75-foot one and the English a 250 footer. The latter will be used at lower frequencies, however, and might transmit pulse to mars.