Imagine Magazine - Johns Hopkins - November/December 2008 - (Page 42) ➜ 15 Hunters than stars, typically only one optics coronagraph is under ten-thousandth of a star’s light is construction right now by a team blocked. Measuring the amount of astronomers, of which I am a of this slight dimming lets us part, from California, New York, directly see a planet’s size. Similar and Canada. Our instrument, the measurements in the infrared Gemini Planet Imager, should can reveal a planet’s temperature. be operational by early 2011. Its improved sensitivity will let Better yet, measuring transits us observe Jupiter-mass planets in multiple wavelengths of light much closer to their parent stars; lets us detect gases in planets’ we will be able to see planets with atmospheres based on how masses and orbits comparable to different gases absorb different Gliese 581 c, shown from the perspective of a possible moon, is thought to be a rocky world Jupiter and Saturn in our own wavelengths. When NASA’s about 1.5 times the radius of Earth. Its temperature is uncertain, yet it resides near the star’s solar system. Just as with radial Hubble and Spitzer Space habitable zone, making the existence of oceans and lakes a possibility. velocities, there is a scientific race Telescopes were designed, such spurring us onwards, with a team measurements were beyond of our European colleagues and friends building a similar instrument astronomers’ wildest dreams—yet those two telescopes have proven of their own. If all goes well, in a few years these instruments will be champions at the extraordinarily precise measurements needed to turn snapping photos and measuring the atmospheres of planets by the distant eclipses into newfound knowledge. hundred. This coming spring, those two spacecraft will be joined by a new Beyond that, the future gets hazier. NASA is today planning a series space telescope called Kepler, a special-purpose craft optimized precisely for measuring planetary transits for many more stars far more of Exoplanet Probe missions over the next few years, building toward an ambitious Terrestrial Planet Finder program around perhaps 2020 carefully than ever before. If all goes according to plan, Kepler will or beyond. That hypothetical craft would use techniques similar to be able to detect the one-part-in-a-million microeclipses caused by coronagraphs to directly image Earth-like planets in search of alien an Earth-like planet passing in front of a star. By surveying hundreds life signs, but the precise details of how to actually build such a thing of thousands of stars over the next few years, Kepler boldly aims remain far from clear. We seek no less than to answer at long last those to produce a galactic census of Earth-mass planets orbiting in the age old questions: How common are worlds like our own? Do any “habitable zone” where temperatures are right for life like ours. distant suns shine down on worlds teeming with alien life, perhaps even intelligent life? The chances are greater than ever that these Toward Pale Blue Dots These and other indirect methods have unmasked for us the secrets questions will be answered within our lifetimes. Doing so will take the of several hundred worlds, but astronomers have never given up the combined efforts of many hard-working scientists and brilliant young dream of seeing such worlds directly. Such observations would let planet hunters. Maybe they’ll even be answered by some of you! i us find new planets with a single snapshot, instead of the long years of waiting required for radial velocity or transit work, and would Marshall Perrin is an astronomer working at UCLA. Originally from open the way to much more detailed studies of atmospheres and Annapolis, MD, he attended CTY Lancaster from 1993–1995. After gradcompositions. Over the past decade, we have nurtured adaptive optics uating from Harvard, he headed west to California and earned a Ph.D. technology, which can correct for the blurring and twinkling caused in astronomy from UC Berkeley in 2006. His other interests include sciby the Earth’s turbulent atmosphere, and developed instruments called ence education, biking and backpacking, environmental conservation, coronagraphs that can block out almost 100 percent of a star’s light and science fiction. For more of his writing, check out his bimonthly while still letting an orbiting planet be seen. For several years, such column in the online magazine Strange Horizons (http://strange instruments have surveyed nearby stars to no avail—until now. horizons.com ). On the very day that I am writing this, a team of Canadian astronomers using the Gemini Telescope’s adaptive optics system has just presented their very first direct image of a probable planet Word Wise Solution orbiting a young sunlike star. It’s a weird object, “Seen for the first time through a backyard telescope, ringed eight times more massive than Jupiter but Saturn, icon of the otherworldly, orbiting shockingly far from its parent star, ten is the vision most likely to turn times Neptune’s distance from our sun, where an unsuspecting viewer into an the greater separation from the star made it astronomer forever.” easier to detect. —Dava Sobel, The Planets This pale dot is but the tip of the iceberg. A much more advanced adaptive 42 imagine November/December 2008 ©Lynette Cook ➜ http://strangehorizons.com http://strangehorizons.com
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