Exoplanets – terrestrial bodies that exhibit Earth-like characteristics and their possible inhabitants – have long been conjured and popularized in science fiction, from unearthly places as imagined by Arthur C. Clarke, to deceptively logical TV shows with legions of cult-followers like Star Trek. , Finding a terrestrial planet that lies within the habitable zone of a star, a region where liquid, water and possibly life might exist cannot quite be covered in a 45-minute episodic adventure.
No one knows this better than Dr. William Borucki, the Science Principal Investigator for NASA’s spacecraft Kepler – named after the 17th-century astronomer, Johannes Kepler, founder of the Laws of Planetary Motion. Bespectacled and partially bald (in his official NASA picture), he’s somewhat of an expert in the field of identifying exoplanets. A firm believer in the project, he advocated like it was his job, but really, it was his life’s passion. He weathered four proposal rejections beginning from the early 90s, so you could say that it became episodic after the first.
That is, until December 2001, where he successfully convinced (exhausted) a judging panel to cough up the $600 million needed to execute the idea. A date was set, 2007 was the year to anticipate. “It’s the most important endeavour NASA is undertaking, in my opinion,” ventured Dr. Borucki in a 2007 NASA interview; the article mentioned a launch date of around November 2008. “We are trying to find man’s place in the universe. The first step in doing that is finding Earth-like planets. Ultimately, we’ll travel to the stars to see who is there,” he predicted in the same interview. Kepler (the first spacecraft of its kind) was launched in March 2009.
Out in space, Kepler’s primary function is to survey a portion of the Milky Way galaxy for signs of Earth-size planets. The manner wherein it detects the planets needs an explanation: as a planet orbits past its star, it causes a tiny dip in the star’s light output. Because of the relative size differences between a star and a planet, this passing seems like a mere “wink” to the casual observer from many light years afar.
To measure the small variations of brightness from the star, a custom built photometer (or light meter) needed to be put on board. Said spying glass comes equipped with a lens, a primary mirror, and a charge-coupled device array. The CCD is an image recording sensor made up by an array or grid of light-sensitive cells. The image becomes a mosaic of pixels with brightness and colour information for each pixel.
Kepler’s star field, (its field of view, if you like) is the constellations Cygnus and Lyra. Over 100,000 stars in this region alone were pre-selected for this spacecraft’s scrutiny, chosen due to their similarities with our Sun, in terms of size, mass, temperature, and brightness (brighter stars generally allow for greater transit detection). To date, more than 2,740 exoplanet candidates have been filed. Optimistically, Dr. Borucki expects that up to 90% of the listed exoplanet candidates will eventually be confirmed.
“We are finding an absolutely enormous range of planet types,” from planets with a density of Styrofoam, to planets two or three times the size of Jupiter, to a binary star system (Codename: Tatooine; Luke Skywalker’s home planet in the films Star Wars). “It has come as quite a surprise,” said an awestruck Dr. Borucki in a recent interview for the Independent UK. Equally amazed was Kepler’s Mission Manager, Roger Hunter, “Kepler has found planets and planetary systems that made astronomy firsts,” he wrote in the mission’s official blog for the month of March, “The first four years have been an amazing ride. We are sure that Kepler’s best discoveries are yet to come.”
Be that as it may, none of the discoveries thus far have exhibited the Earthly facets of harbouring an atmosphere suited to simple forms of life, let alone to evolved dolphins. “There are about 40 to 50 planetary candidates in the habitable zone but there are no Earth-sized planets there. We have not yet found Earth-sized planets in the habitable zone,” Dr. Borucki solemnly admits, adding that it’s impossible to tell if there are indeed other Earths out there at this point in the mission.
Because of the high ratings Kepler has been getting thus far, Popular Mechanics sat Dr. Borucki down for a Q&A session. When asked about the future of Kepler, the always-reliable Dr. Borucki had some exquisite insights to share, “What the mission is designed for, and I’m going to be a little facetious here, is to be the most boring mission ever launched,” clarifying that its main function was to take pictures “over and over again”. Ending the discussion with a classic Borucki touch, he added: “We’ll find out the answer to the question ‘Are earths common?’…And if the answer is yes, life is probably common, too. And that means that we can move forward to new missions that go and explore those planets and find life on those planets.”
While Kepler is yielding auspicious results confirming the existence of Earth-like orbs in the celestial night sky, Exoplanetary Science is still in its embryonic stages, satellite beneficiaries (stellar evolution, etc.) included. In the meantime, NASA’s banker, the US Government Treasury, and the citizens of the world can collectively anticipate the day Curiosity will tweet “Just stepped on an amoeba, LOL”. And I envision the quick-witted Kepler’s riposte – “Gosh, what a twit.”