Stargazers

Astronomers have long passed the stage of studying the heavens directly with simple, visible light. Last week, at Madison, Wis., the American Astronomical Society learned of some new, fancy capers which light can be made to cut.

Drs. Joel Stebbins and A. E. Whitford, of the University of Wisconsin, cast an infra-red ray of hope on astronomy's bitterest sorrow : the invisibility of the Milky Way's nucleus. Even with small telescopes, astronomers can study the galaxies, gigantic clouds of stars which float far off in space. At their centers most galaxies have tight star clusters which may contain much of their mass. These nuclei facinate astronomers, for within them, they suspect, are conditions which exist nowhere else in the universe.

But when astronomers try to look at the center of the "home" or Milky Way galaxy to which our own sun belongs, they see practically nothing. It is comparatively near, but dark, cosmic clouds frustrate their peering telescopes, and it is estimated that less than 1/1,000 of the ordinary blue photographic light from the galaxy center gets through the obscuring interstellar dust.

Infra-red rays pierce some clouds ; so Dr. Walter Baade of Mt. Wilson, Calif, photographed the proper part of the sky with infra-red light. His plate showed a dim, ghostly shape (see cut). Drs. Stebbins and Whitford, encouraged, used infra-red light of still longer wave length. They attached a photoelectric cell and an infra-red filter to the Mt. Wilson 60-inch telescope and swept it back & forth across the area where the nucleus ought to be. Their calculations showed a strong elliptical bulge. The happy astronomers did not claim that this was the Milky Way's actual nucleus. But they were sure that it must be the dense central region of the galaxy, which no human eye can see.

Star Discs. Stars are so far away that even in the most powerful telescope they look like mathematical points. Astronomers have measured the diameters of some with an elaborate device called an interferometer." But they yearn for a better method.

Luckily, many stars are eclipsed by the moon. When this happens, the star does not vanish instantaneously. Instead, it makes the moon cast, for one-fiftieth of a second, a ribbed shadow of bright-and-dark "diffraction bands." By measuring these, the star's disc can be measured. But the bands are 30 feet apart, and they race past a telescope's lens at more than 1,000 miles per hour. No photographic plate or observer's eye is big enough or fast enough to catch them.

So Dr. Whitford hitched another photoelectric cell to a telescope, this time Mt. Wilson's giant 100-incher. As the bands raced past, they knocked from the cell a fluctuating electric current. Dr. Whitford shot the current into an "oscilloscope" to make the fluctuations visible. He took a picture of their pattern of peaks and valleys, then measured the diffraction bands, and from them calculated the diameter of the star.

How Stars Grow. One of the things which astronomers worry about is why most of the matter in the universe is clotted into widely separated stars. Why did it clot in the first place? And are the clots (stars) still forming out of shattered matter? At Madison, Dr. Lyman Spitzer of Yale told his theory:

Astronomers agree that the space between the stars is not entirely empty, but contains tiny grains of matter and exceedingly thin gases. The grains, said Dr. Spitzer, radiate heat so quickly that their temperature is always near absolute zero (-459DEG p.). But the gases consist of separate atoms or molecules. For them, heat is velocity. They do not lose it easily by radiation. Dr. Spitzer calculated that the temperature of the thin gas in space might frequently be as high as on the surface of an average star: 20,000DEG F.

When cold grains of matter are present, said Dr. Spitzer, the gas molecules collide with them. This reduces the molecules' velocity (the same thing as their temperature). Then they adhere to the grains, making them bigger. Eventually the grains get big enough to attract one another by gravitation. The little clot grows to a bigger clot. In a billion years or so, a star is born.

This file is automatically generated by a robot program, so reader's discretion is required.