The search for alien civilizations in space has expanded to cover the entire sky.

A new radio receiver started running in Argentina on Friday, the anniversary of Columbus' discovery of the new world."Today represents the opening up of half of the universe to the search by the human species for extraterrestrial intelligence," said astronomer Carl Sagan, president of the Planetary Society.

"You have to be made of wood not to be interested in knowing whether we're alone in the universe," Sagan said by phone from Ithaca, N.Y., where he is a professor at Cornell University. "Here we are for the first time in human history when it's technically possible to find out. And it's very cheap.

"Wouldn't we be ashamed of ourselves if the answer was there for the taking and we were too shy to look?"

The Pasadena-based Planetary Society, which advocates space exploration, financed the supercomputer-controlled radio receiver and signal analyzer with $150,000 raised from its 125,000 members in more than 100 nations.

The 8.4-million-channel receiver, about the size of two large refrigerators, is called Megachannel Extraterrestrial Assay II, or META II. It is located at Argentina's Institute of Radioastronomy, 30 miles southeast of Buenos Aires.

Steven Spielberg, who directed the films "E.T., the Extra-Terrestrial" and "Close Encounters of the Third Kind," donated $100,000 for META I.

The META project is the world's most powerful operating search for alien radio signals, although nothing has been heard so far.

About 100 people watched as the institute's director, Raul Colomb, pointed one of the institute's 98-foot-wide radiotelescope dish antennas toward the Southern Cross, a major Southern Hemisphere constellation, as the receiver was switched on Friday morning.

The new receiver is capable of listening to the heart of our Milky Way galaxy.