Alvin Wallace, age 17, of Casper, Wyo., for his question:

WHEN WERE THE MAFFEI GALAXIES DISCOVERED?

The Maffei galaxies, often called Maffei 1 and Maffei 2, are two large star systems. They probably belong to the group of galaxies that include the earth's galaxy, the Milky Way. The Maffei galaxies remained unknown until 1968 because they are hidden by dense clouds of cosmic dust and gas in the earths galaxy.

The Maffei galaxies were discovered in 1968 by an Italian astronomer named Paolo Maffei, for whom they were named. Maffei photographed the galaxies through a telescope by using film sensitive to infrared rays, the invisible heat rays given off by the galaxies. Infrared rays, unlike light rays, can penetrate dust clouds.

In 1971, astronomers at several California observatories determined the approximate size and shape of the Maffei galaxies.

Each of the Maffei galaxies measures from 50,000 to 100,000 light years in diameter. Maffei 1, the brighter of the two systems, may consist of as many as 100 billion stars. Maffei 2 has only about 10 billion stars.

Astronomers classify Maffei 1 as an elliptical galaxy because of its oval shape. Maffei 2 resembles a flattened coil and is classified as a spiral galaxy.