Astronomers have spotted something through telescopes seen only once in a hundred years -- the explosion of a star in a nearby galaxy.

Such an explosion is called a supernova, and some of the ones sighted over the centuries have been recorded in ancient religious writings as powerful omens, because the brightest ones can light the night sky like another moon and can even be seen in the daytime.

The star of Bethlehem, which in Christian teachings led three wise men to the birthplace of Jesus, may have been a supernova, according to some accounts.

The recent supernova was first seen on the night of Nov. 30 by two Chilean astronomers, Marina Wischnjewsky and Jose Maza of the University of Chile. By Dec. 10, Dr. Anthony Moffatt of the University of Montreal, using the 158-inch telescope at the Inter-American Observatory near LaSerena, Chile, had confirmed the sighting.

The supernova was discovered in a galaxy called Fornax A. The star that exploded was not normally visible to instruments and had to grow up to to 50 times brighter before it was noticed Nov. 30. Once it was seen, astronomers watched it grow still brighter, to four times the brightness at first sighting, before it began to die out.

A supernova explosion occurs when the interior of an old star collapses inward, creating an immense thermonuclear explosion that gives off light greater than the billions of stars which make up the entire surrounding galaxy. g

The explosions of supernovas create from light elements, such as hydrogen and helium, many heavier ones, such as carbon, oxygen and nitrogen. These heavier elements are thrown explosively into space to form new stars and planets. The elements that make up the earth and its life are believed by some scientists to have been formed in an explosion of a supernova.