Planetary sweepstakes heat up
Fifty 'exoplanets' have been discovered in five years
(CNN) -- The ancient Greeks called them "wandering stars," a reference to the roguish ways of certain heavenly bodies with no fixed cosmic address.
About 2000 years later, the Renaissance telescope-toter Nicholas Copernicus stunned his fellow stargazers with the brainstorm that those streaking "stars" were actually "planets," performing their galactic duty by rotating around the Sun.
Now, members of the International Astronomers' Union gathering this week and next at their 24th triennial conference in Manchester, England, are pushing the cosmic envelope further.
The IAU's unveiling on Monday of 10 newly detected planets outside our solar system -- including a Jovian-sized orb just 10.49 light years from Earth -- heralds the latest phase in an intensifying scavenger hunt for the astronomers' Holy Grail: life beyond Earth, preferably on a place that looks like Earth.
Smaller is better
Among the planets added to the celestial roster on Monday, one bears an uncanny resemblance to Jupiter. Lying 478 million kilometers from its own star, it is about the same distance as Earth's sun from the asteroid belt.
The discovery has fueled speculation that there could be a smaller, earth-sized planet within the vicinity of Epsilon Eridani, the central star in the constellation Eridanus.
In astrophysics, smaller is better. In May, a team of astronomers from Geneva announced the discovery of what they called eight "very low-mass companions to solar-type stars." The tally included two so-called brown dwarfs, or stillborn stars, which do not classify as planets.
Monday's announcement from the IAU has raised the stakes further in the extra-planetary sweepstakes.
"We're all pretty sure that they're out there (Earth-like planets)," said Philip Diamond, director of the Merlin national facility at the Jodrell Bank observatory at the University of Manchester.
"In the next generation of telescopes, in say 15 years time, we actually hope to image Earth-like planets, to see if they have an atmosphere, and to determine the elements of that atmosphere."
Fifty 'exoplanets' in five years
It took astronomers two millennia to find and identify the nine planets in Earth's solar system -- an achievement capped by the chance discovery of icy, far-flung Pluto in 1930.
But it's taken them less than five years to catalogue nearly 50 extrasolar planets -- or "exoplanets."
Recent forays by telescope and satellite into galaxies beyond Earth's Milky Way have spawned speculation that life in some form may exist on a jovian moon, Europa, that astronomers believe may conceal an ocean, or within the crevices of the martian landscape.
Speculation has also centered on another moon of Jupiter, Ganymede, and on sun-scorched Venus, which probably wasn't always as hot as it is now.
Now scientific advances are allowing scientists to broaden their cosmic horizons. But astronomers are still working blind, in a sense, since they cannot directly see the planets they claim to have discovered.
The latest spate of extra-solar planetary findings hinged on detecting subtle shifts in star light caused by an orbiting planet's gravitational tug. The breakthrough in the use of such technology came in October 1995, when a team of astronomers from the Geneva Observatory discovered an exoplanet revolving around a star known as 51 Pegasi.
A tip-off from a dimming star
Today, no fewer than half a dozen teams of astronomers from the United States and Europe are manning high-powered radial and optical telescopes in hopes of homing in on an Earth-like planet.
With scientific advances allowing ever more precise methods of measuring these wobbles, astronomers say, they are hopeful they may be on the cusp of more significant discoveries.
Last year, a slight dimming of light from star HD 209458, roughly 150 light-years from Earth, offered astronomers the most iron-clad evidence to date of the existence of a planet outside Earth's solar system.
Alan Boss, an astrophysicist with the Carnegie Endowment of Washington, D.C., and author of Looking for Earths, said the mere fact "we are finding planets by the bucketful these days" implies that the search for a life-supporting planet is anything but a quixotic pursuitof the Carnegie Institute of Washington.
"We might have to search perhaps a hundred or a thousand stars to find them; we are going to have to look around," he said.
Part of the problem for astronomers trawling for terrestrial-like planets is their inability -- at present -- to see them directly. Most planets are undetectable in the glaring spotlight of their own suns, which can be millions of times brighter than the planets they illuminate.
That means the existence of extra-solar planets can only be inferred from nuances in the way a star behaves -- nuances that are more easily detectable when the planet under scrutiny is a giant, gaseous body such as Jupiter.
Not a planet after all
All the earnest star searching has not come without a few cosmic false alarms. In April, NASA made an embarrassing retraction when it admitted that a bright dot astronomers had initially identified as a possible "rogue planet" was probably just a dim star.
But for all the doubts, astronomers believe that the slew of recent star discoveries is a prelude to bigger -- or rather smaller -- things to come.
Geoff Marcy, of the University of California at Berkeley, and a member of one of the teams behind the latest planet discoveries told a scientific publication, UniSci, in March that astronomers eyes are getting keener as they scan the skies.
"It's like looking at a beach from a distance," Marcy said. "Previously, we only saw the large boulders, which were Jupiter-sized planets or larger. Now we are seeing the 'rocks,' Saturn-sized planets or smaller.
"We still don't have the capability of detecting Earth-like planets, which would be equivalent to seeing pebbles on the beach."
Diamond, of the Jodrell Bank observatory, believes that capability isn't too far off and that planetary discoveries may soon draw little more than a cosmic yawn.
"At some point they will become so routine that there will be no press releases. There are billions and billions of planets out there."
Scientists reveal nine new planets - August 7, 2000
Astronomers say new planet might hold clues about Earth - August 5, 2000
Hubble image of so-called 'rogue' planet is actually a star - April 7, 2000
Mars lander listening party tuning in to red planet - February 4, 2000
International Astronomical Union
Royal Astronomical Society
The Extrasolar Planets Encyclopaedia
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