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Finding New Worlds: Theoretical Conjecture Versus Hands-on Astronomy

BOULDER, Colorado - There is ongoingtheoretical debate regarding how and where to spot other worlds circlingdistant stars. And there are new ground and in-space observational tools thatare locking into real-time data.

Presently,200-plus known extrasolar planets have been found--mostly huge, gas-giants like Jupiter within our own solar system of Sun-orbiting planets.Given these discoveries--just within the last 10 years or so--under whatconditions can we expect terrestrial planets to crop up? Moreover, just howcommon are habitable planets in the universe?

Planetscouting scientists met here January 26-28 at a media workshop sponsored by the University of Colorado's Center forAstrobiology to share theories as well as new observational information.

Whilethe planetary plotting thickens, it's also a stew of opposite conclusions,assumptions, talk of new or weird physics, along with downright uncertainties.It all adds up to a collegial clash between those that predict contrasted to observationalfindings.

Debate revived and revitalized

What'snow taking place is that extrasolar planet researchers are shifting into highgear given ground and space-based tools. That being the case, will theories onspotting Earth-like worlds be overtaken by actual observation?

"Absolutely," responded Alan Boss, a research staff member at the CarnegieInstitution's Department of Terrestrial Magnetism in Washington, D.C.

"Theoristsspent several decades debating the formation of our solar system, where thebasic physical characteristics had been known for centuries...number of planets,masses, separations, etc. That debate has now been revived and revitalized inthe last decade by the ever-increasing information we are learning fromextrasolar planetary systems," Boss explained to

Bosssaid that the focus of the debate right now is on giant planets--becausethose are the ones that have been found to date in greatest abundance.

Theorists are parasites

Butlast December's liftoff of Europe's COnvection, ROtation and planetary Transits (COROT)telescope--along with next year's slated takeoff of NASA's Kepler mission--signal near future discoveries of hot and warm Super-Earths and habitableEarths, Boss suggested.

"Wecan expect an equally contentious debate over how to explain their formationand

orbitalevolution, though perhaps a debate that is not quite so contentious as thecurrent debate over giant planet formation, given the two wildly differentformation mechanisms being considered for them," Boss said.

Atheory that explains the previously known might be plausible, Boss continued,but unless it can predict the unknown, it is of little value - and even thenmay eventually be proven incorrect by further observations.

"Theoriststruly are parasites...and derive their sustenance from the growing body ofobservational evidence about other planetary systems," Boss concluded.

Synergistic understanding

"Thestandard theorist line is never believe in an observation unless it has beenconfirmed theoretically," said Jack Lissauer, a space scientist in thePlanetary Systems Branch at NASA's Ames Research Center near Silicon Valley, California. "I'm trained as atheorist...but I'm interested in observations."

Lissaueris co-discoverer of the first four planets known to orbit about faint M dwarfstars. He also co-discovered two faint outer rings and two small inner moons ofthe planet Uranus.

Tocorrespond to the real universe, researchers must be constrained byobservations, Lissauer pointed out. But in order to guide observations and havesome idea of where to look, as well as how best to design planet-huntinginstruments, that's where theorists come in.

"It'ssynergistic," Lissauer said. "You have to have both to be able to understandyour observations theoretically and confirm your theories through observation."

Planet migration

"Boththeory and observations are key," concurred Sean Raymond, a NASA postdoctoralresearcher here at the University of Colorado's Center for Astrobiology and Center forAstronomy and Space Astrophysics.

"Observationsmake discoveries, but theory is needed to interpret them," Raymond said.

Forinstance, "hot Jupiters" were discovered starting in 1995, Raymond emphasized.Most of the exoplanets identified to date are these gas giants in a stableorbit very close to their parent star.

"Itwas certainly strange to have giant planets so close to their stars," Raymond Theory is what probed the origin of hot Jupiters, he said,and came up with the idea of planet migration, the current model being thatthese planets form father out and migrate in to their current locations.

Cosmic cooking class

Considerit a lesson bubbling out of cosmic cooking class 101.

"It'slike having dinner at someone's house. Observations can tell you the specificingredients that went into the meal. But theory can figure out exactly how thepieces go the dish was cooked," Raymond explained.

Raymondprojected outward over the next decade. He foresees the finding of Earthanalogs.

"We'regoing to be seeing all these little small guys. That's going to pretty cool,"Raymond said. Furthermore, more and more of them will be found in unexpectedand varied environments, and around different type stars once thought asimpossible locales.

"Anytimeanybody predicts, 'ooh, this could never happen'...then you'll find somebody todisprove it," Raymond advised.

Light of a living planet

MargaretTurnbull, an astronomer at the Space Telescope Science Institute in Baltimore, Maryland is on a pursuit tolook for life elsewhere. She has created a catalog of nearby stars--dubbed"HabCat"--that could host life forms similar to those on Earth. This catalogis now the target list for the search for extraterrestrial intelligence.

Atthe Space Telescope Science Institute, Turnbull is also the principleinvestigator of a proposed mission to deploy a small telescope on the Moon.That instrument would be designed to look back at the Earth and provide insightinto how the light of a living planet changes as continents and oceans pass inand out of view, as weather patterns move, and as seasons change.

Thequest for extrasolar worlds is cutting edge research and therefore iscontentious, Turnbull told

"Itis because you are really operating at the edge of human knowledge and humanunderstanding," Turnbull noted. "Every new observation we make to some extentoverthrows what we thought that we knew."

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