NASA SHIFT, NEW PLANETS EXCITE ASTRONOMERS.

Byline: Robert S. Boyd Knight-Ridder News Wire

By their nature, scientists distrust research based on only a single example or experiment. They don't feel confident about their findings until they have been confirmed by repeated tests.

That makes it hard for scientists who study the nature of life. Earthlings have had only one case to study - our own planet.

Until now.

Exultant astronomers learned last week of the discovery of two planets with characteristics similar to Earth's - a revelation that greatly increases the probability that life exists elsewhere in the universe. What's more, they listened enthusiastically as Dan Goldin, NASA administrator, laid out his ambitious vision for the next 25 years - including an all-out search for life on other planets.

"We see ourselves at the gateway to a new era in science," said Geoffrey Marcy, the San Francisco State University astronomer who was co-discoverer of the latest planets. "Now we can compare our own nine planets to their planetary cousins in other solar systems."

Said Goldin: "This touches the human spirit, not just the intellect. I get quite emotional about it."

Like partners in a rocky marriage, astronomers and the space agency have suffered through an uneasy relationship over the years.

Scientists needed the powerful telescopes and other tools provided by the National Aeronautics and Space Administration. But they resented the billions NASA spent on engineering feats, boosting people up and down in shuttles (six were on a mission in the Endeavour this past week), tinkering with a huge space station of dubious scientific value.

Goldin's pledge to the American Astronomical Society that NASA's emphasis is changing won him a hero's welcome last week. The search for life elsewhere that Goldin promised has long been astronomers' dream, but never before has it rated so high on NASA's list of priorities.

"There has been a sea change at NASA," said Robert Brown, a senior astronomer at the Space Telescope Science Institute in Baltimore. "For the first time in 40 years, NASA and the scientific community are seizing on the idea of discovering planets like Earth as a central goal."

The detection of two new planets - raising to six the population of known planets outside our solar system - was only one of a number of stunning discoveries announced to the 1,400 astronomers gathered for their semiannual meeting.

Other highlights of the week included:

Evidence that half or more of the mysterious "dark matter" making up 90 percent of the universe consists of burned-out stars known as white dwarfs. Even though white dwarfs are too small and cold to be visible from Earth, their presence was revealed by the way they interfered with the light coming from more distant stars.

Hubble Space Telescope photographs of the farthest, faintest galaxies ever observed, created when the universe was less than one-tenth of its present age. The photos vastly increased the estimated number of galaxies in the universe from 10 billion to 50 billion, each containing from 50 billion to 100 billion stars.

The first picture of the actual surface of a star other than the sun. A Hubble image showed an enormous hot spot on the face of Betelgeuse, a bright star 500 light-years away in the constellation Orion. It is the largest star in the sky visible to the naked eye, but until now had appeared only as a point of light, not a disk.

More Hubble images portraying the death of stars in unprecedented detail and foreshadowing how our own sun will end 5 billion years from now. The pictures showed dying stars that have blasted their atmospheres into space, creating weirdly shaped nebula and leaving behind only a cold white dwarf.

The two new planets - gaseous giants three and eight times larger than Jupiter - were detected orbiting around two sunlike stars, one in the Big Dipper and the other in the Constellation Virgo, 35 light-years (210 trillion miles) from Earth.

The stars, known as 47 Ursae Majoris and 70 Virginis, are visible to the naked eye, but the still unnamed planets could be detected only by measuring the tiny wobble they caused in the orbit of their stars.

Although four other planets have been spotted around other stars since 1992, these were the first to offer a possibility that they could harbor complex organic molecules, the building blocks of living organisms. Their temperature is believed to be warm enough to permit liquid water - perhaps rain or even oceans - an essential condition for life as we know it on Earth.

The four planets previously discovered are considered uninhabitable. Three of them are orbiting a highly radioactive neutron star that would make life impossible. The fourth is so close to its star and so hot - 1,800 degrees Fahrenheit - that water would be vaporized.

Though it is highly unlikely that even primitive living organisms, such as bacteria, exist on these Jupiter-scale planets, their discovery caused jubilation among the astronomers. It convinces them that planets must be common among the trillions of stars in the universe, making it probable that humans are not alone. Keener instruments just coming into use should be able to see Earth-size planets more conducive to life.

"This is a very exciting time," Brown said, "the culmination of almost 500 years of intellectual history since Copernicus suggested that Earth was not the center of the universe."

Goldin predicted: "In 25 years, we'll be able to image an Earth-size planet and see oceans, clouds and mountain ranges."

In outlining his goals for the next 25 years, Goldin acknowledged that NASA had lacked a grand strategy since the first manned landing on the moon almost 30 years ago.

"We haven't had a vision, a road map, a strategic plan for NASA," he said. "We've had five-year plans - we need a 25-year plan."

Goldin invited the astronomers to contribute their ideas and criticisms to the long-range program, which is due to be completed by the summer of 1997. He said the goal was to answer three basic questions:

How do galaxies, stars and planets form and evolve?

Are there other Earthlike planets that show signs of life?

What is the origin and ultimate fate of the universe?

The astronomers were delighted, because these are precisely the goals many of them share. Several questioned, however, whether Congress would provide enough money to carry them out, or if Goldin was just trying to make them feel good.

But despite the looming budget crunch, the astronomers' mood was distinctly upbeat.

"We will look back on 1995 as a wonder year," predicted Neville Woolf, an astronomer at the University of Arizona. "We have begun a new study of planets around other sunlike stars. This is a journey of a thousand miles. The next step is to find Earthlike planets with Earthlike atmosphere."