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The Secret Lives of Stars 2004 WWW.SCIAM.COM COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC. SCIENTIFIC AMERICAN Volume 14, Number 4 The Secret Lives of Stars 2004 3 Letter from the Editor YOUTH 4 The First Stars in the Universe BY RICHARD B. LARSON AND VOLKER BROMM Exceptionally massive and bright, the earliest stars changed the course of cosmic history. 12 Fountains of Youth: Early Days in the Life of a Star BY THOMAS P. RAY To make a star, gas and dust must fall inward. So why do astronomers see stuff streaming outward? 18 Companions contents to Young Stars BY ALAN P. BOSS The surprising finding that even the youngest stars commonly exist in sets of two or three has revised thinking about the birth of star systems. 26 The Discovery of Brown Dwarfs BY GIBOR BASRI Less massive than stars but more massive than planets, brown dwarfs were long assumed to be rare. New sky surveys, however, show that the objects may be as common as stars. 42 THE SECRET LIVES OF STARS COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC. 34 92 MIDLIFE OLD AGE 34 The Stellar Dynamo 76 Supersoft X-ray Stars and BY ELIZABETH NESME-RIBES, SALLIE L. BALIUNAS AND DMITRY SOKOLOFF Supernovae BY PETER KAHABKA, EDWARD P. J. VAN DEN HEUVEL AND Sunspot cycles—on other stars—are helping astronomers SAUL A. RAPPAPORT study the sun’s variations and the ways they might Supersoft sources—which spew unusually low-energy affect Earth. x-rays—are now thought to be white dwarf stars that The Fury of Solar Storms siphon matter from their stellar companions and then, in 42 many cases, explode. BY JAMES L. BURCH Shock waves from the sun can endanger Earth’s 84 Binary Neutron Stars satellites and astronauts. BY TSVI PIRAN When Stars Collide The inevitable collapse of these paired stellar remnants 50 generates runaway heating that, for a few weeks, emits BY MICHAEL SHARA more light than an entire galaxy. When two stars smash into each other, it can be a very pretty sight. Once considered impossible, these 92 The Brightest Explosions occurrences have turned out to be common in certain galactic neighborhoods. in the Universe BY NEIL GEHRELS, LUIGI PIRO AND PETER J. T. LEONARD 58 X-ray Binaries Every time a gamma-ray burst goes off, a black hole is born. BY EDWARD P. J. VAN DEN HEUVEL AND JAN VAN PARADIJS When ultradense neutron stars feed on their more sedate companions, the binary systems produce outpourings of x-rays and drastically alter the evolution of both stars. Cover illustration by Don Dixon Scientific American Special (ISSN 1048-0943), Volume 14, Number 4, 2004, published by Scientific 68 Magnetars American, Inc., 415 Madison Avenue, New York, NY 10017-1111. Copyright © 2004 by Scientific BY CHRYSSA KOUVELIOTOU, ROBERT C. DUNCAN AND American, Inc. All rights reserved. No part of this issue may be reproduced by any mechanical, photographic or electronic process, or in the form of a phonographic recording, nor may it be stored CHRISTOPHER THOMPSON in a retrieval system, transmitted or otherwise copied for public or private use without written permission of the publisher. Canadian BN No. 127387652RT; QST No. Q1015332537. To purchase Magnetized so intensely, some stars alter the very nature additional quantities: U.S., $10.95 each; elsewhere, $13.95 each. Send payment to Scientific American, Dept. STARS, 415 Madison Avenue, New York, NY 10017-1111. of the quantum vacuum. Inquiries: fax 212-355-0408 or telephone 212-451-8890. Printed in U.S.A. 2 THE SECRET LIVES OF STARS COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC. ® letter from the editor Established 1845 The Secret Lives of Stars is published by the staff of Scientific American, with project management by: Exposé on the Stars EDITOR IN CHIEF: John Rennie EXECUTIVE EDITOR: Mariette DiChristina ISSUE EDITOR: Mark Fischetti ISSUE CONSULTANT: George Musser FOR PURE THEATRICS and spectacle, Hollywood ce- ART DIRECTOR: Edward Bell ISSUE DESIGNER: Patti Nemoto lebrities have nothing on PHOTOGRAPHY EDITORS: Bridget Gerety Small, the denizens of the heav- Emily Harrison, Smitha Alampur ens. Stars are born, live and PRODUCTION EDITOR: Richard Hunt die in fiery and fascinating COPY DIRECTOR: Maria-Christina Keller COPY CHIEF: Molly K. Frances ways—ways that we have COPY AND RESEARCH: Daniel C. Schlenoff, only recently been able to Michael Battaglia, David Labrador, Sara Beardsley study in greater detail, like EDITORIAL ADMINISTRATOR: Jacob Lasky so many swarming papa- SENIOR SECRETARY: Maya Harty razzi, using the long-range ASSOCIATE PUBLISHER, PRODUCTION: lenses created by improved William Sherman MANUFACTURING MANAGER: Janet Cermak techniques and new, sharp- ADVERTISING PRODUCTION MANAGER: Carl Cherebin er observatories. PREPRESS AND QUALITY MANAGER: Silvia Di Placido We’ve observed some PRINT PRODUCTION MANAGER: Georgina Franco PRODUCTION MANAGER: Christina Hippeli eye-popping behavior from CUSTOM PUBLISHING MANAGER: Madelyn Keyes-Milch these brazen orbs. As with ASSOCIATE PUBLISHER/VICE PRESIDENT, CIRCULATION: many glamorous beings, Lorraine Leib Terlecki stars often pair off, but the CIRCULATION DIRECTOR: Katherine Corvino FULFILLMENT AND DISTRIBUTION MANAGER: two may blow apart—liter- Rosa Davis ally—one star ripping the ENCOUNTER with a tempestuous starlet tears apart our sun. VICE PRESIDENT AND PUBLISHER: Bruce Brandfon shine from its former part- WESTERN SALES MANAGER: Debra Silver ner in a highly public display. It seems that only about half the stars live as cou- SALES DEVELOPMENT MANAGER: David Tirpack ples—no better than the average state of human relationships. Or consider the WESTERN SALES DEVELOPMENT MANAGER: Valerie Bantner wondrous strange doings of the magnetar, a name itself worthy of a character SALES REPRESENTATIVES: Stephen Dudley, in the blockbuster X-Men films. These intensely magnetized stars emit huge Hunter Millington, Stan Schmidt bursts of magnetic energy that can alter the very nature of the quantum vacu- ASSOCIATE PUBLISHER, STRATEGIC PLANNING: um. Like rebels without a cause, they are furiously active for only a short time: Laura Salant PROMOTION MANAGER: Diane Schube after 10,000 years they wink out. We’ve also been able to see how, after a long RESEARCH MANAGER: Aida Dadurian era of flamboyant x-ray emission, x-ray binaries settle down to become some PROMOTION DESIGN MANAGER: Nancy Mongelli of the most steady, unchanging entities in the cosmos. Not all of these celestial GENERAL MANAGER: Michael Florek BUSINESS MANAGER: Marie Maher objects make it as luminaries, however. We may feel some sympathy for brown MANAGER, ADVERTISING ACCOUNTING AND dwarfs, failed stars that glow so dully nobody could even find one until 1995. COORDINATION: Constance Holmes In this special edition from Scientific American, we invite you to forget about DIRECTOR, SPECIAL PROJECTS: everyday life to spend some time with the stars. In the pages that follow, you’ll Barth David Schwartz find the latest gossip on the glitterati, written by the astronomer shutterbugs MANAGING DIRECTOR, ONLINE: Mina C. Lux themselves. Although the stars have revealed more than ever, they’ve been OPERATIONS MANAGER, ONLINE: Vincent Ma SALES REPRESENTATIVE, ONLINE: Gary Bronson careful not to tell all, lest we grow bored with their antics. As authors Chryssa DIRECTOR, ANCILLARY PRODUCTS: Diane McGarvey Kouveliotou, Robert C. Duncan and Christopher Thompson so aptly put it in PERMISSIONS MANAGER: Linda Hertz “Magnetars”: “What other phenomena, so rare and fleeting that we have not MANAGER OF CUSTOM PUBLISHING: recognized them, lurk out there?” We can hardly wait to find out. Jeremy A. Abbate CHAIRMAN EMERITUS: John J. Hanley CHAIRMAN: John Sargent PRESIDENT AND CHIEF EXECUTIVE OFFICER: Mariette DiChristina Gretchen G. Teichgraeber Executive Editor VICE PRESIDENT AND MANAGING DIRECTOR, INTERNATIONAL: Dean Sanderson Scientific American VICE PRESIDENT: Frances Newburg MARK A. GARLICK [email protected] www.sciam.com THE SECRET LIVES OF STARS 3 COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC. THEFIRST STARS IN THE UNIVERSE Exceptionally massive and bright, the earliest stars changed the course of cosmic history We live in a universe that is full of bright objects. On a clear night one can see thousands of stars with the naked eye. These stars occupy mere- ly a small nearby part of the Milky Way galaxy; tele- scopes reveal a much vaster realm that shines with the light from billions of galaxies. According to our current understanding of cosmology, howev- er, the universe was featureless and dark for a long stretch of its early history. The first stars did not appear until perhaps 100 million years after the big bang, and nearly a billion years passed before galaxies proliferated across the cosmos. Astron- BY RICHARD B. LARSON AND VOLKER BROMM omers have long wondered: How did this dramat- ILLUSTRATIONS BY DON DIXON ic transition from darkness to light come about? 4 SCIENTIFIC AMERICAN Updated from the December 2001 issue COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC. EARLIEST COSMIC STRUCTURE mmostost likely took the form of a network of filaments. The first protogalaxies, small-scale systems about 30 to 100 light-years across, coalesced at the nodes of this network. Inside the protogalaxies, the denser regions of gas collapsed to form the first stars (inset). COPYRIGHT 2004 SCIENTIFIC AMERICAN, INC. After decades of study, researchers The Dark Ages to longer wavelengths and the universe have recently made great strides toward THE STUDY of the early universe is grew increasingly cold and dark. As- answering this question. Using sophisti- hampered by a lack of direct observa- tronomers have no observations of this cated computer simulation techniques, tions. Astronomers have been able to ex- dark era. But by a billion years after the cosmologists have devised models that amine much of the universe’s history by big bang, some bright galaxies and show how the density fluctuations left training their telescopes on distant galax- quasars had already appeared, so the first over from the big bang could have ies and quasars that emitted their light stars must have formed sometime before.
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