Instruments aboard a U2 aircraft have discovered evidence of gigantic galaxies outside our galaxy that are so large they are pulling ours toward them at a speed of more than one million miles an hour.

The clusters of galaxies appear to be beyond the constellation Virgo, trillions of miles away from Earth. So vast might the clusters of galaxies be that they could be two billion light years across, an area equal to a tenth of the observable universe.

The supercluster of galaxies is invisible to optical telescopes on Earth, in part because the galaxies are so far away and in part because they are abscured by our own Milky Way galaxy, which contains more than 200 billion stars.

While there is now no direct evidence for the existence of these galaxies, scientists believe that if a supercluster is indeed there beyond Virgo it contains more than 1 percent of the stars in the entire universe.

The instruments that discovered evidence of the supercluster were microwave radiometers that were looking for slight differences in temperature of the interstellar gas that pervades the universe. The radiometers were looking across the entire sky at the so-called background radiation left over from the Big Bang that created the universe 20 billion years ago.

This background radiation has long been measured at three degrees above absolute zero, so that what the instruments were looking for was slight changes either up or down in that temperature to see if they could spot distant galaxies that could not be seen from Earth. Galaxies invisible from Earth would make the background radiation appear cooler than three degrees, partly because their gravitational pull would be drawing interstellar gas in their direction.

Scientists at the University of California at Berkeley believe the U'2s instruments detected -- in the direction of the constellation Virgo -- temperatures cool enough to suggest the Milky Way is moving in the direction of Virgo at twice the speed it should be. This would place the velocity of the Milky Way at a speed of more than one million miles an hour.

This does not mean the milky Way will collide with these distant galaxies or be sucked into them; the space between galaxies is far too vast.

Even though the U2 evidence is indirect, other X-ray observations from satellites appear to confirm the existence of enormous objects beyond the constellation Virgo.

A British satellite named Ariel, which mapped the sky in the X-ray region, sees a much brighter X-ray signal beyond Virgo than it gets from anywhere else in the heavens. The signal from Virgo suggests that there is a "large lump" of matter in space far beyond Virgo where X-rays are concentrated, possibly by gravitational pull. This would explain why the Milky Way is moving toward Virgo at such a high rate of speed since the gravitational pull exerted by the invisible supercluster of galaxies would be enough to draw the Milky Way toward it at a high rate of speed.