Strange New Worlds: The Search for Alien Planets and Life beyond Our Solar System - Softcover

Jayawardhana, Ray

Softcover

ISBN 10: 069115807X ISBN 13: 9780691158075

Verlag: Princeton University Press, 2013

Inhaltsangabe

An insider's look at the cutting-edge science of today's planet hunters

In Strange New Worlds, renowned astronomer Ray Jayawardhana brings news from the front lines of the epic quest to find planets-and alien life-beyond our solar system. Only in the past two decades, after millennia of speculation, have astronomers begun to discover planets around other stars-thousands in fact. Now they are closer than ever to unraveling distant twins of the Earth. In this book, Jayawardhana vividly recounts the stories of the scientists and the remarkable breakthroughs that have ushered in this extraordinary age of exploration. He describes the latest findings--including his own-that are challenging our view of the cosmos and casting new light on the origins and evolution of planets and planetary systems. He reveals how technology is rapidly advancing to support direct observations of Jupiter-like gas giants and super-Earths-rocky planets with several times the mass of our own planet-and how astronomers use biomarkers to seek possible life on other worlds.

Strange New Worlds provides an insider's look at the cutting-edge science of today's planet hunters, our prospects for discovering alien life, and the debates and controversies at the forefront of extrasolar-planet research.

In a new afterword, Jayawardhana explains some of the most recent developments as we search for the first clues of life on other planets.

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Über die Autorin bzw. den Autor

Ray Jayawardhana is professor and Canada Research Chair in Observational Astrophysics at the University of Toronto, as well as an award-winning science writer.

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"Jayawardhana's small book is a gem. It brings readers up to date on the rapidly progressing quest for exoplanets and their potential inhabitants, and also interweaves the very human details about the people behind these discoveries. Read this book if you want a picture of how modern astronomy and astrobiology are helping to calibrate our place in the universe. A most delightful read."--Jill Tarter, director of the Center for SETI Research

"Jayawardhana brings the latest cutting-edge science to all those astounding science-fictional visions of alien worlds, showing us that the universe is every bit as exciting as the masters of science fiction have always claimed. It's no accident that his title invokes the opening of the original Star Trek. In this terrific book, he boldly goes out into the galaxy, showing us strange--and wondrous--new worlds."--Robert J. Sawyer, Hugo Award-winning author of Wake, Watch, and Wonder

"If you have ever wanted to know how astronomers are going to find an Earth-like planet, this engaging book explains it all. Not only is Strange New Worlds fantastic storytelling about the checkered and dramatic history of exoplanet discovery, but it also gives a compelling description of the path to future discoveries."--Sara Seager, author of Exoplanet Atmospheres

"Strange New Worlds is a very satisfying book that does a thorough and excellent job of tracing the discovery and characterization of extrasolar planets. It is the only popular-level book that gives full, up-to-date, and in-depth coverage of one of the most exciting and fast-moving fields of scientific research."--Greg Laughlin, coauthor of The Five Ages of the Universe: Inside the Physics of Eternity

"This is quite a good book. Its greatest strengths are the clarity of the writing; the thorough, technically accurate, and very up-to-date coverage of the material; and of course the fascinating topics the author presents."--Edwin L. Turner, Princeton University

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STRANGE NEW WORLDS

The Search for Alien Planets and Life beyond Our Solar System

By Ray Jayawardhana

PRINCETON UNIVERSITY PRESS

Copyright © 2011 Ray Jayawardhana
All rights reserved.

ISBN: 978-0-691-15807-5

Contents

Chapter 1 Quest for Other Worlds The Exciting Times We Live In............
1
Chapter 2 Planets from Dust Unraveling the Birth of Solar Systems.........
16
Chapter 3 A Wobbly Start False Starts and Death Star Planets..............
46
Chapter 4 Planet Bounty Hot Jupiters and Other Surprises..................
67
Chapter 5 Flickers and Shadows More Ways to Find Planets..................
94
Chapter 6 Blurring Boundaries Neither Stars nor Planets...................
123
Chapter 7 A Picture's Worth Images of Distant Worlds......................
149
Chapter 8 Alien Earths In Search of Wet, Rocky Habitats...................
172
Chapter 9 Signs of Life How Will We Find E.T.?............................
203
Glossary...................................................................
229
Selected Bibliography......................................................
239
Afterword to the Paperback Edition.........................................
245
Index......................................................................
251
Acknowledgments............................................................
263
About the Author...........................................................
265

Excerpt

CHAPTER 1

Quest for other worlds

The Exciting Times We Live In

We are living in an extraordinary age of discovery. Aftermillennia of musings and a century of false claims, astronomershave finally found definitive evidence ofplanets around stars other than the Sun. A mere twentyyears ago, we knew of only one planetary system forsure—ours. Today we know of hundreds of others.What's more, thanks to a suite of remarkable new instruments,we have peered into planetary birth sitesand captured the first pictures of newborns. We havetaken the temperature of extrasolar giant planets andespied water in their atmospheres. Numerous "super-Earths"have been found already, and a true Earth twinmight be revealed soon. It is still the early days of planetsearches—the "bronze age" as one astronomer put it—butthe discoveries have already surprised us and challengedour preconceptions many times over. What's atstake is a true measure of our own place in the cosmos.

At the crux of the astronomers' pursuit is one basicquestion: Is our solar system—with its mostly circularorbits, giant planets in the outer realms, and at least onewarm, wet, rocky world teeming with life—the exceptionor the norm? It is an important question for everyone of us, not just for scientists. Astronomers expectto find alien Earths by the dozens within the next fewyears, and to take their spectra to look for telltale signsof life perhaps before this decade is out. If they succeed,the ramifications for all areas of human thoughtand endeavor—from religion and philosophy to art andbiology—are profound, if not revolutionary. Just thefact that we are potentially on the verge of so momentousa discovery is in itself remarkable.

Worlds Beyond

Human beings have speculated about other worlds andextraterrestrial life for millennia, if not longer. Someancient civilizations considered the heavens to be theabode of gods. Others believed that souls would migrateto the Sun, the Moon, and the stars after death. By thefifth century BC, a number of Greek philosophers consideredthe likelihood of multiple worlds and proposedthat heavenly bodies are made of the same material asthe Earth. Those ideas were central to their doctrineof atomism, the idea that the entire natural world wasmade up of small, indivisible particles. Metrodorus ofChios, a student of Democritus, is said to have written:"A single ear of corn in a large field is as strange as asingle world in infinite space." In the year 467 BC, abright fireball appeared in the skies of Asia Minor, andfragments of it fell near the present-day town of Gallipoli.The event affected the thinking of many, includingthe young philosopher Anaxagoras of Clazomenae whowrote: "The Sun, the Moon and all the stars are stoneson fire.... The Moon is an incandescent solid havingin it plains, mountains and ravines. The light which theMoon has is not its own but comes from the Sun." (Healso said that the purpose of life is to "investigate theSun, Moon and heaven.") The Roman poet Lucretiusbelieved in "other worlds in other parts of the universe,with races of different men and different animals."

Other prominent Greek philosophers, most notablyPlato and Aristotle, espoused the opposing view—thatthe Earth is unique. The Earth-centric model of thecosmos, based on the teachings of Aristotle and Ptolemy,gained prominence over time and dominated theEuropean worldview until the late Middle Ages. Conveniently,the privileged position claimed for our planetand humankind suited the church teachings. There waslittle discussion of extraterrestrial life, with a few exceptions.The tide started to turn with the publication ofNicolas Copernicus's influential volume On the Revolutionsof Celestial Bodies just before his death in 1543.He posited that the Sun occupied the center of the universe,thus displacing the Earth from its unique niche.

But the true revolution occurred with the inventionof the telescope at the beginning of the next century.Galileo's 1610 discovery of four moons circling Jupiterproved the existence of heavenly bodies that did notorbit the Earth. He also showed that Venus exhibiteda full set of phases, just like the Moon, as predicted byCopernicus's Sun-centered model. Perhaps even moredramatic was the revelation from Galileo's telescopic observationsthat the Moon was quite similar to the Earthin many ways. His beautiful sketches of the lunar landscapeshow mountains and valleys. Here was another"world" in its own right, with familiar topography.

I remember the first time the concept of another worldentered my mind when I was a child. It was during awalk with my father in our garden in Sri Lanka, where Igrew up. He pointed to the Moon and told me that peoplehad walked on it. I was astonished: the idea that onecould walk on something in the sky boggled my mind.Suddenly that bright light in the sky became a place thatone could visit. To be sure, it was the possibility of adventure,rather than the great philosophical implicationsof there being other worlds, that impressed me. Lookingback, that moment has had a defining impact on the pathI have taken in life. Like many kids, I dreamt of becomingan astronaut. That desire fostered my interest in scienceand eventually led me to a career in astrophysics.

The first time I heard about planets being detectedaround other stars was in the summer of 1991, whileI was an intern at The Economist in London. The scienceeditor, Oliver Morton, mentioned that astronomerswere about to announce a planet orbiting a stellar cindercalled a pulsar. I didn't quite grasp the significance—andwas a bit annoyed that the planet story bumped fromthat week's issue an article I had written! Six monthslater, that particular claim was retracted, but a differentpulsar with planets was found by then. A few yearslater, I interviewed several astronomers searching forJupiter-like planets around normal stars for a news itemin Science magazine. Despite fifteen years of searching,they had not found any as of 1994, so some wonderedwhether Jupiters might be rare.

Common or Rare?

Early ideas about the origin of the solar system impliedthat planets are a natural outcome of the Sun'sbirth—thus they should be common around other starstoo. In 1755, the Prussian philosopher Immanuel Kantproposed that planets coalesced out of a diffuse cloudof particles surrounding the young Sun. His model attemptedto explain the order of the planets: the innerones were denser because heavier particles gatherednear the Sun while the outer planets grew bigger becausethey could collect material over a larger volume.Unfortunately, soon after his book was printed, Kant'spublisher went bankrupt, and not even King Frederickthe Great, to whom it was dedicated, got to see Kant'sambitiously titled book Universal Natural History andTheory of the Heavens: An Essay on the Constitutionand Mechanical Origin of the Whole Universe accordingto Newton's Principles.

Forty years later, the French mathematician PierreSimon Laplace came up with a somewhat different versionof the "solar nebula" model. He suggested thata fast-spinning young Sun cast off rings of material,out of which the planets condensed. Again, the implicationis that the same could happen with other stars.Laplace's scenario accounted for the planets orbitingthe Sun in the same plane and the same direction. Heinterpreted Saturn's rings as evidence in favor of histheory, adding that they may condense into moons inthe future. When Laplace presented his five-volumetreatise on the solar system to Napoleon Bonaparte,the latter taunted him about not mentioning God in hiswork. Laplace famously replied, "Sir, I have no need ofthat hypothesis."

The nebular theory ran into various difficulties in theearly 1900s. Two of its critics—University of Chicagoscientists Thomas Chrowder Chamberlin and ForestRay Moulton—proposed a replacement in 1905. Theyclaimed that a passing star had induced large eruptionson the Sun, which in turn ejected material into orbit.As the material cooled, it condensed into planets andnumerous small bodies. A decade later, the British astronomerJames Jeans advocated a similar idea. If theywere right, there would be few planetary systems inthe Galaxy, because close encounters between stars areextremely rare. However, serious objections raised byother astronomers eventually led to the demise of thestellar-encounter model for solar system formation. Bythe 1940s, the German physicist Carl Friedrich vonWeizsäcker revived the nebular theory. The outlines ofthe modern picture of how planets form, as we will seein chapter 2, resemble Kant's early ideas. That's goodnews for planet hunters.

Daunting Challenge

Astronomy is not like the other natural sciences. Withfew exceptions, its practitioners do not get to put theirquarry under a microscope or experiment with it. Thestars are so distant that there is little chance of measuringtheir composition in situ or bringing back samplesfor laboratory studies. Instead, for the most part, astronomershave to make the best of the feeble light reachingtheir telescopes from remote celestial bodies. The challengefacing planet sleuths is even greater. Stars shinelike floodlights, compared with the planetary embers intheir midst. Seen from afar, even a giant planet like Jupiterwould be hundreds of millions of times fainter thanthe Sun in visible light. So to find extrasolar planets,astronomers have had to develop clever methods thattake advantage of the physics of light and gravity.

When Auguste Comte, the prominent French philosopherwho is often regarded as a founder of modernsociology, considered the limits of human knowledge,he assumed it was pretty safe to declare the intrinsicproperties of stars, let alone their unseen planets, to bebeyond our ken for eternity. In his 1835 monographCours de philosophie positive, Comte wrote: "On thesubject of stars, all investigations which are not ultimatelyreducible to simple visual observations are ...necessarily denied to us. While we can conceive of thepossibility of determining their shapes, their sizes, andtheir motions, we shall never be able by any means tostudy their chemical composition or their mineralogicalstructure.... [W]e shall not at all be able to determinetheir chemical composition or even their density.... Iregard any notion concerning the true mean temperatureof the various stars as forever denied to us."

Comte's timing could not have been much worse.Unknown to him, several scientists across Europe werealready making fundamental discoveries about the natureof light that would soon prove him wrong. Thoseadvances not only paved the way for measuring thecomposition and temperature of stars, but they also underpintoday's exploration of planetary systems in theirmidst.

Decoding Light

One critical breakthrough was the discovery by theGerman-born English astronomer William Herschelin 1800 of a new form of light, while experimentingwith a prism and several thermometers. He spread sunlightinto a rainbow of colors with the prism, as IsaacNewton had done two centuries earlier, and took thetemperature of the different colors. To his surprise,the temperature was highest just beyond red, where hecould not see any sunlight. He correctly surmised that anew form of radiation, which he called "calorific rays"from the Latin word for heat, must be responsible. Inother experiments, he found that these rays were reflected,refracted, transmitted, and absorbed the sameway as visible light. His discovery of what we now callinfrared radiation proved the existence of types of lightinvisible to our eyes. Now astronomers depend heavilyon detecting light in all its forms—the entire electromagneticspectrum spanning from meter-long radiowaves to highly energetic gamma rays—to investigatecosmic phenomena.

A second breakthrough had to do with mysteriousdark lines seen among the rainbow colors of the solarspectrum. The English physician-turned-chemist WilliamHyde Wollaston had noticed them as early as 1802.He mistakenly interpreted them as natural boundariesbetween the colors. The German optician Joseph vonFraunhofer re-discovered these lines in 1814 and nearlyunraveled their profound connection to the compositionof stars.

Orphaned at twelve, and too frail to become a woodturner as he had hoped, Fraunhofer took up an apprenticeshipwith a Munich glassmaker. His master treatedhim harshly and denied him access to books and school.One day in 1801, the glassmaker's workshop collapsed,burying the young apprentice under its rubble for severalhours. The disaster turned out to be a blessing indisguise for Fraunhofer, since the prince elector of Bavaria,who was present at the rescue, became his patron.With the prince's help, Fraunhofer was able to join aglassworks factory where he quickly became one of theworld's top optical-instrument makers. He invented newdevices to study the properties of light, including a "diffractiongrating" with diamond-carved grooves only0.003 millimeters apart. It enabled him to measure thewavelengths of light in different colors more preciselythan anybody had before. With the help of these devices,he not only recorded hundreds of dark lines in the solarspectrum but also noted their similarities to lines seenin spectra of certain flames in the laboratory. He eventook spectra of a number of bright stars in the nightsky, including Sirius and Capella, and remarked on thesimilarities and differences between their line patterns.Fraunhofer came remarkably close to deciphering thatstars are made of the same stuff as the world aroundus. He died prematurely at age thirty-nine from tuberculosis,which may have been aggravated by the metalvapors he inhaled near glass-melting furnaces. Appropriatelyenough, the epitaph on his tomb reads Approximavitsidera: "He brought the stars closer."

Two scientist friends working together in Heidelberg,Gustav Kirchhoff and Robert Bunsen, resolved themystery of Fraunhofer lines (as they are now called) in1859. They confirmed what others had suspected: eachelement produces its own distinct pattern of spectrallines—sort of a unique fingerprint or calling card—andthe same lines "exist in consequence of the presence, inthe incandescent atmosphere of the sun, of those substanceswhich in the spectrum of a flame produce brightlines at the same place." Thus Comte's declaration wasrefuted within a mere quarter century. Scientists couldnow tell what the stars are made of, though the roleof atomic structure in producing spectral lines wouldnot become clear until the development of quantum mechanicsin the early twentieth century.

The news of Kirchhoff and Bunsen's discovery spreadquickly in the western world. Self-taught astronomerand retired silk merchant William Huggins heard of itin London in 1862, at a lecture on spectrum analysis.The speaker was William Allen Miller, a King's Collegechemistry professor who happened to be Huggins'sneighbor. The news "was to me like the coming upon aspring of water in a dry and thirsty land," he reminisceddecades later. "A sudden impulse seized me, to suggestto [Miller] that we should return home together. On ourway home I told him of what was in my mind, and askedhim to join me in the attempt I was about to make, toapply Kirchhoff's methods to the stars."

Retired from his trade, Huggins had built a privateobservatory in a south London suburb. Following Miller'stalk, he carried out spectroscopic studies of stars,nebulae, and even meteors. He showed that nebulae andgalaxies, both of which appear fuzzy to the naked eyeand small telescopes, were in fact different beasts: theformer exhibited emission lines characteristic of gaswhile the latter had spectra similar to stars. His investigationswere bold and technically challenging endeavorsat the time, and their success brought him well-deservedrecognition from his peers. In later years, he was ablyassisted by his wife Margaret Lindsay Huggins, whohad learned the constellations from her grandfatheras a child and built a spectroscope herself, based on amagazine article, before the two met. The Hugginses'investigations marked the birth of modern astrophysics,shifting the focus away from charting positions, shapes,and apparent motions of celestial objects to understandingtheir physical nature.

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Excerpted from STRANGE NEW WORLDS by Ray Jayawardhana. Copyright © 2011 by Ray Jayawardhana. Excerpted by permission of PRINCETON UNIVERSITY PRESS.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Details zur Ausgabe

• Verlag: Princeton University Press
• Erscheinungsdatum: 2013
• Sprache: Englisch
• ISBN 10: 069115807X
• ISBN 13: 9780691158075
• Einband: Tapa blanda
• Anzahl der Seiten: 278
• Kontakt zum Hersteller: Nicht verfügbar
• Verantwortliche Person: Nicht verfügbar