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It's been a mere 15 years since astronomers discovered the first planet outside of our solar system orbiting a sun-like star. In that time, the catalog of known planets has grown to more than 500 and scientists expect that number to grow dramatically in the coming years.
That first world found in 1995, 51 Pegasi b, was a massive and gaseous planet, approximately the size of Jupiter and orbiting closer to its host star than Mercury does to our own sun. As planet detection techniques have improved, scientists have been able to find smaller and smaller planets, but their Holy Grail still remains: finding Earth's twin.
This week, hundreds of astronomers will descend on Flagstaff to debate and discuss that hunt. Their conference, which is being sponsored by NASA's Jet Propulsion Laboratory and its PlanetQuest Exoplanet Exploration Program, is titled "Exploring Strange New Worlds."
The week-long gathering will center on professional talks and collegial elbow-rubbing, but on Monday, the conference will throw open its doors to the public with a lecture by Geoff Marcy, a veteran planet hunter and U.C. Berkeley professor of astronomy.
His talk at NAU's Prochnow Auditorium will address the search for other Earths and the likelihood of intelligent life in our cosmic neighborhood.
Marcy was a member of one of the groups that discovered the first exoplanets and is now on NASA's Kepler Space Telescope team, which has already identified more than 1,200 potential planets and is widely expected to discover the first Earth-like exoplanet.
"Astronomers have not yet found a single planet that reminds us of home," Marcy said in an interview with the Daily Sun this week. "In particular, we haven't found any planets that have a rocky surface on which water can puddle, and water serves as a cocktail mixer for life."
DIPS AND WOBBLES
Those early discoveries were made using a technique called radial velocity. The method relies on tiny star wiggles that are characteristic of the gravity from an orbiting planet tugging the star very slightly toward it.
Kepler takes another approach. The spacecraft is designed to stare at one patch of sky and take pictures of 150,000 stars without blinking. That data are then combed for tiny dips in light from any individual star.
If a star is tilted toward Earth just right, when an orbiting planet passes in a line between the star and our line of sight it will result in what astronomers call a transit.
Marcy compares it to sitting in a living room and having a fly land on a nearby light. The insect would block a minuscule amount of light from reaching you, but if you had sufficient equipment, you could not only detect the dip, but also deduce the fly's exact size from how much light was blocked.
Of course, the actual process of discovery isn't so easy. There are any number of unusual circumstances that can trick astronomers into making a false planet detection, so Kepler keeps watching for the planet to pass in front of the star again and again. Meanwhile, astronomers like Marcy also point Earth-bound telescopes at the same stars until they can confirm the candidate planet.
TRANSCOSMOS EXPLORATION
Kepler will provide astronomers with the first census of exoplanets. The telescope will examine less than 1 percent of the night sky, but Marcy compares the project to a political poll. While they have a small sample region, the patch of sky they examine should be no different than any other random area, so it will give astronomers an idea of how many Earth-like planets are out there.
The spacecraft, which started making observations in late 2009, is expected to find thousands of planets over the course of its 3 1/2-year mission and some have predicted that tens of thousands more will be discovered by subsequent missions over the coming decades.
"It's comparable to the transoceanic voyages of the 15th century," Marcy said. "Those explorers indeed were hoping to find new worlds and said they had found a new world. Of course, it was just a new continent. We're actually finding new worlds."
Data from the Kepler mission were recently used to deduce that some 50 billion planets likely exist in our Milky Way Galaxy, so those spacecraft will only be able to find a minute fraction of all the worlds.
"It's an extraordinary era in the history of science" Marcy said. "You might even say it's an extraordinary era in the history of humanity. We now, for the first time, are finding other worlds that remind us of the world we've lived on for the past few million years."
Reach the reporter at ebetz@azdailysun.com or 556-2250.
Posted in Local on Tuesday, May 3, 2011 9:00 am Updated: 8:36 am. | Tags:
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