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It has been more than 450 years since Copernicus demonstrated that Earth isn't at the centre of things, but for most people the news has yet to sink in. Poor, deluded Earthlings, you think you're special: You fixate on a single rocky planet just because it's yours and act as though the night sky is an ornament to your existence rather than a monumental challenge to your uniqueness.

Watch out, world: Sara Seager plans to prove that we're not alone.

The wiry 39-year-old Canadian is a precocious pioneer in the hunt for exoplanets, the celestial bodies orbiting far-off stars. As a member of the U.S. National Aeronautics and Space Administration's Kepler mission team, she is engaged in a long-term quest to shift the very underpinnings of our consciousness and prove that there's life outside our tiny solar system.

"For thousands of years, people have wondered if there's life beyond Earth," she says during a recent expedition to the Perimeter Institute in Waterloo, Ont.

"We're the first generation with the technical capability to show that there is. Potentially we'll be the society that discovers the first extrasolar life - and in 1,000 years, people will remember our era as the starting point of the interstellar journey they've embarked on."

Earth-centred complacency is no longer an option as new information from the orbiting Kepler space telescope transforms the meaning of the night sky. How many planets does our single galaxy contain? About 50 billion, Kepler's chief scientist declared last week, of which 500 million are in the habitable zone where life could exist.

Now, it's up to planetary detectives such as Sara Seager to turn Kepler's not-so-distant dreams into reality.

What kind of person goes searching for signs of life in remote galaxies? For Sara Seager, the starting point was her uncomfortable relationship with this small world of ours.

"I may look like I fit in, but I'm a born outsider. I realized this when I was 5 or 6, sitting in the back of the station wagon with a bunch of other girls on the way home from school. I looked at them and realized that I had nothing in common with these people. But it wasn't a sad thought: Because if you don't fit in, then you don't have to do normal things."

Prof. Seager gives full credit to her father, a suburban Toronto general practitioner turned hair-transplant pioneer, who urged her to take on new projects and pursue abnormal passions, including astronomy.

"My Dad really pushed me to be a successful person. He was constantly doing things to make me uncomfortable, to push my boundaries, then push them again."

Working with her students at the Massachusetts Institute of Technology, she is now preparing to launch a fleet of nanosatellites that will monitor the brightest stars in the sky, intensifying the hunt for planets that most closely resemble Earth.

"This is going to change the paradigm of space telescopes," she says with the breezy certainty of a born paradigm-buster.

She has been called "one of the guiding lights in the field of exoplanet research" by planet-hunter Debra Fischer of Yale University."

A Kepler colleague, Geoff Marcy, observes that the young Canadian astrophysicist "has pioneered several entirely new areas of planetary science, including the detection of Earth-like planets around other stars and the assessment of their chemical composition as gleaned from the light coming from their atmospheres."

Appropriately for a woman who feels constrained by a single solar system, Prof. Seager doesn't hold back on her scientific ambitions. "We want to change the way people see their place in the universe," she says with cosmic immodesty. "My aim is to take people and point at a star you can see with the naked eye in a really dark sky and say, 'That star has a planet like Earth.' "

Cautionary warning for alien trackers: The discovery of a small, rocky, Earth-like planet is only the starting point for finding the first hints of distant life, such as water vapour in the atmosphere. And even then, the kind of life water might generate doesn't need to reach ET standards: Single-celled bacteria will do quite nicely in Prof. Seager's mission.

"I'm in this to find life, but the life I'll find won't be aliens," she says, marking a clear separation from the Sigourney Weaver style of extraterrestrial confrontations.

By the standards of explorers such as Prof. Seager, Earth lost its self-centred primacy a long time ago. Copernicus's revelation that Earth revolved around the sun was a good start. Then came evidence that the sun was just another star in our galaxy. When Edwin Hubble revealed in 1924 that the Milky Way was just one of many galaxies, the feelings of smallness - or greatness, depending on one's sense of wonder - could only increase.

The first exoplanets were discovered in the mid-1990s. More than 500 nearby extrasolar planets were subsequently identified, using ingenious techniques that measure a star's "wobble" in relation to a planet's gravitational pull or its temporary drop in starlight as an orbiting planet passes by. The latest Kepler study, focusing on a tiny corner of the sky, adds 1,235 more likely candidates - with the caveat that astronomy isn't currently capable of confirming their actual planetary qualities. Still, it's clear to Prof. Seager that the odds are narrowing: If planets are as common as Kepler indicates, then the chances of finding Earth's counterpart get better and better.

Our star alone harbours eight planets. How many stars are there in our galaxy? About 100 billion. And how many galaxies are there in the universe? Let's say about 100 billion.

Those are numbers to unsettle the savviest Vegas oddsmaker. Even the Vatican has had to rethink the kinds of truth that could be out there: Prof. Seager was part of a group that met with the Pope's advisers to discuss the possibility of life on other planets - much like Copernicus's challenges to church doctrine, exoplanet researchers are disturbing theology's comfort zone.

Getting more women like herself into science is one of her latest passions - she has worked with the cosmetics firm L'Oréal to lobby U.S. Congress on the issue. But reflecting on her own upbringing, she believes that even the best-intentioned programs of social re-engineering will require a tough-love side: Push a person's boundaries far enough, and looking for life among the exoplanets seems almost routine.

Yet suppose life exists: That doesn't mean humans will be high-fiving their extrasolar counterparts any time soon. Hitching a ride on the kind of plodding spacecraft we now send to Mars, a traveller would need 500,000 years to reach the nearest star. Even the kind of souped-up craft that exists in the wildest dreams of the most optimistic engineers, travelling at one-10th the speed of light, would still take 43 years to get to the nearest star, plus another 43 years for the return trip. Any volunteers?

Which is why telescopes do most of the work. The Kepler telescope studies 150,000 stars and looks for subtle changes in a star's brightness - an indication that a planet may be passing by in a regular orbit. Researchers can then study the character of these exoplanets remotely by analyzing how the star's bright light changes as it passes through the planet's atmosphere.

Thinking big creates big problems, however. Rocky Earth-like planets tend to be small and dim compared with their much brighter host stars. Prof. Seager describes her field's fundamental problem with a striking image: "Finding an Earth twin around a sun-like star is like trying to see a firefly fluttering less than a foot from a huge searchlight - when the searchlight is 2,600 miles away."

Discouraged? Maybe you're not cut out for exoplanet research and its non-stop reality checks.

"The sobering thought," Prof. Seager says, "is that the number of stars we can actually look at in order to identify their properties is quite small."

She sounds discouraged, this unrelenting champion of the seemingly impossible. And then she faces down the doubts that confront a woman determined to expand our Earth-based mentality.

"If I were to take a harsh look at reality, and say, 'What are my chances of finding another Earth?' - that's not a pretty picture. So in order to get up every day and do my job and get excited about it, I have to believe we're going to do it - and do everything in my power to bring it about."

John Allemang is a feature writer for The Globe and Mail.

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