Jessica Salyer, age 15, of Great Falls, Mont., for her question:

WHAT IS THE VERY LARGE ARRAY?

Very Large Array is the name of the largest array of radio telescopes in the world. The collection of telescopes, also called VLA, is located near Socorro, New Mexico, and consists of 27 dish antennas placed in a Y shaped pattern, with arms 13 miles long.

VLA is operated by the National Radio Astronomy Observatory and became fully operational in October 1981, although parts of the array had been used to make observations for several years.

The VLA operates on the principle of aperture synthesis, a radio astronomy technique in which several small antennae are used together to build up the same image in the sky that a much larger antenna would receive.

The total gathering power of the 27 antennae, each having a diameter of 82 feet, is equal to that of a single antenna 17 miles in diameter.

The maximum resolution at a wavelength of 0.512 inches equals the resolution of an optical telescope with a reflector of about 36 inches in diameter.