© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION PE1 © JonesThe & Bartlett Quest Learning, LLC Ahead © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION1 © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEO ORN THE DISTRIBUTION NIGHT OF MARCH 23, 1993, amateur astronomerNOT David FOR Levy SALE photographed OR DISTRIBUTION part of Comet Shoemaker-Levy 9 the sky near the planet Jupiter. His friends, fellow astronomers Carolyn Shoemaker was broken by Jupiter’s and her husband Eugene Shoemaker, spotted something unusual in the picture: a gravitational forces into comet that had broken up into about 20 pieces. The comet became known officially as more than 20 fragments (bottom photo), all follow- Comet Shoemaker-Levy 9 (the ninth comet discovered by these three sky-watchers) ing the same path toward and unofficially© Jonesas the “string & Bartlett of pearls” Learning, comet. LLC © Jonesa &collision Bartlett with Jupiter. Learning, LLC When astronomersNOT FOR announced SALE OR the DISTRIBUTION news of the comet on June 1, 1993, theyNOT had FORCourtesy SALE of Hubble OR DISTRIBUTIONSpace traced its path closely enough to tell that it had come under the influence of Jupiter’s Telescope Comet Team powerful gravitational field. They had deduced that the comet was pulled apart by and NASA. This photo of Jupiter’s gravity in July of 1992. They predicted that the comet would crash into Jupiter (top photo) shows Jupiter on or about July 25, 1994. the impact spots left by © JonesBy October& Bartlett 1993, Learning, astronomers LLC had refined their predictions.© Jones The comet & Bartlettwas Learning,some of the fragments.LLC Courtesy of STScI/NASA. NOTthen FOR stretched SALE out OR over DISTRIBUTION a distance of 3 million kilometers (1.8NOT million FOR miles) SALE in orbit OR DISTRIBUTION around Jupiter. The first piece was predicted to hit Jupiter at 4:01 PM (Eastern day- light savings time in the United States) on July 16, and the last piece was predicted to hit at 4:00 AM on July 22, 1994; however, nobody knew whether the impacts would be big or small or even observable by telescopes on Earth. © Jones & Bartlett ByLearning, the time of LLC the predicted impacts, the entire© Jones world & was Bartlett watching, Learning, linked to- LLC NOT FOR SALEgether OR DISTRIBUTION by the Internet and the television. The NOTHubble FOR Space SALETelescope OR was DISTRIBUTIONtrained on 1 © Jones & Bartlett Learning,4TH LLC. NOTPAGES FOR SALE OR DISTRIBUTION. 2 CHAPTER 1 The Quest Ahead Jupiter, as was the Galileo space probe then approaching the Jupiter system, as well as most © Jones & Bartlett Learning,major LLC observatories around the world© Jones and untold & Bartlett numbers Learning, of amateur LLCtelescopes. It has been NOT FOR SALE OR DISTRIBUTIONsaid that more telescopes were aimedNOT at FORthe same SALE spot—Jupiter—than OR DISTRIBUTION ever before or since, and the viewers were not disappointed. Fragment A of the comet hit Jupiter at 4:11 PM Eastern daylight time, only 10 minutes off the prediction made 10 months earlier. Traveling at 60 kilometers/second (130,000 miles/ hour),© Jones each &fragment Bartlett created Learning, a fireball LLC in Jupiter’s upper atmosphere© Jones reaching & up Bartlett as high asLearning, LLC 3000 kilometers (1900 miles) and leaving darkened areas in the atmosphere as wide across as theNOT diameter FOR ofSALE the Earth. OR ScientistsDISTRIBUTION estimated that some of the largerNOT impacts, FOR causedSALE by OR frag DISTRIBUTION- u Six million megatons is about ments about 3 kilometers across, released energy equivalent to 6 million megatons of TNT. 600 times the estimated arsenal (The largest nuclear bomb ever detonated produced a blast equivalent to about 5 megatons.) of the world. The event made front-page headlines around the world, featuring photographs of fireballs © Jones & Bartlettand dark Learning,impact spots LLCacross the giant planet. © Jones & Bartlett Learning, LLC How were astronomers able to predict the time of impact with such accuracy? What did NOT FOR SALEthey learnOR DISTRIBUTIONfrom observing the aftereffects of this stupendousNOT FOR collision? SALE ORMany DISTRIBUTION scientists believe that a similar collision with an asteroid occurred on Earth 65 million years ago, heralding the end of the age of dinosaurs. Since seeing the visible proof of such collisions on Jupiter, many people worry about the chances of further catastrophes on our own planet. Astronomers say © Jones & Bartlett Learning,that the LLC chances of such an event© happening Jones & here Bartlett are roughly Learning, once in 300,000LLC years, but how can they make such a prediction? NOT FOR SALE OR DISTRIBUTIONYou will learn the answers to NOTsome ofFOR these SALE questions OR in DISTRIBUTION this book. You will find that although collisions of comets and planets are very rare in our immediate neighborhood of space, the vast regions of the universe show tremendous activity. Stars are born in dense clouds of gas while other stars explode, spewing forth gas back into space. Galaxies collide over© Jones periods & of Bartlett millions of Learning, years, hurtling LLC stars around at fantastic ©speeds. Jones The & universe Bartlett is Learning, LLC a wild and fabulous showcase, and we will see some of its highlights, looking out from our quietNOT corner FOR called SALE Earth. OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Nothing is rich but the inex- Astronomy is the oldest of the sciences, but it is still changing rapidly today. It is a study haustible wealth of nature. rich in interesting personalities and exciting discoveries. Its long history and recent advances She shows us only surfaces, but make it an excellent example of the progressive nature of science. she is a million fathoms deep. Science is fundamentally a quest for understanding, and in the case of astronomy, the —Ralph ©Waldo Jones Emerson & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC subject of the quest is the entire universe. The study of astronomy covers the full range of NOT FOR SALEmatter OR from DISTRIBUTION smallest to largest. On the small end, NOTit includes FOR atoms SALE and OR their DISTRIBUTION internal work- ings, for astronomers need to know about the nuclear reactions that make stars shine; star A self-luminous celestial this knowledge one day may lead to peaceful applications of thermonuclear reactions. object. Astronomers also study Earth’s neighbors, the planets, and in doing so help us solve problems right here on Earth. For example, a study of weather patterns on Venus and Jupiter has ad- © Jones & Bartlett Learning,vanced LLC our understanding of weather© Jones on Earth. & Bartlett In addition, Learning, studying Mars LLC and Venus helps NOT FOR SALE OR DISTRIBUTIONus understand the past and futureNOT of our FOR own planet.SALE InformationOR DISTRIBUTION we collected using un- u Planets shine by reflected manned spacecraft and Earth-based telescopes has revolutionized our understanding of how sunlight, but stars have an our solar system formed billions of years ago and has evolved since then. In particular, our internal source of energy for their neighborhood was and, to a lesser extent, still is a shooting gallery; we can see the scars of light. We discuss this source collisions on the surfaces of Mercury, the Moon, and other planetary satellites. Understanding the© Jonescomposition & Bartlett of the objects Learning, in our vicinity LLC may one day prove extremely© Jones valuable & Bartlett in our Learning, LLC (nuclear fusion) in our studies of NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION the Sun. efforts to find additional sources of materials for our own survival. The apparent weight- lessness and very low density of space may one day lead to the manufacture of exceptional substances. In some cases, astronomy’s results are more trivial but nevertheless practical: materials developed for the Apollo missions to the Moon are now used in tennis rackets. Astronomers also study the largest groupings of billions of stars, and they ask big ques- © Jones & Bartletttions, the Learning, answers to whichLLC tell us something about© Jonesourselves, & bothBartlett as individuals Learning, and asLLC a NOT FOR SALEspecies. OR Our DISTRIBUTION studies of stars and nebulae help us betterNOT understand FOR SALE the ORnatural DISTRIBUTION cycle of the nebula (plural nebulae) An formation of a star, its evolution, its death, and the recycling of some of its material into a interstellar region of dust and/ new star. or gas. Our studies of galaxies help us better understand the creation and evolution of our universe. Studying astronomy causes us to change our basic outlook as we better appreci- © Jonesgalaxy & A Bartlettgroup of gravitationally Learning, LLC © Jones & Bartlett Learning, LLC bound stars, ranging from a billion ate where humans fit into the magnificent universe. Our species and our planet seem to be NOT FORto perhaps SALE a thousand OR billion stars.DISTRIBUTIONdwarfed by the immensity of the cosmos.NOT FOR In a sense,SALE astronomy OR DISTRIBUTION teaches humility. © Jones & Bartlett Learning,4TH LLC. NOTPAGES FOR SALE OR DISTRIBUTION. 1-1 The View from Earth 3 At the same time, one marvels that humans have been able to learn so much about the © Jones universe& Bartlett in which Learning, we live LLCand that such tiny beings are© ableJones to comprehend & Bartlett the Learning, huge, com -LLC NOT FORplex SALE universe.