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10916_9789813237421_tp.indd 1 19/6/18 1:28 PM Advances in Planetary Science Print ISSN: 2529-8054 Online ISSN: 2529-8062 Series Editor: Wing-Huen Ip (National Central University, Taiwan) The series on Advances in Planetary Science aims to provide readers with overviews on many exciting developments in planetary research and related studies of exoplanets and their habitability. Besides a running account of the most up-to-date research results, coverage will also be given to descriptions of milestones in space exploration in the recent past by leading experts in the field. Published Vol. 3 Planetary Habitability and Stellar Activity by Arnold Hanslmeier Vol. 2 Origin and Evolution of Comets: Ten Years after the Nice Model and One Year after Rosetta by Hans Rickman Vol. 1 Nuclear Planetary Science: Planetary Science Based on Gamma-Ray, Neutron and X-Ray Spectroscopy by Nobuyuki Hasebe, Kyeong Ja Kim, Eido Shibamura and Kunitomo Sakurai KahFee - 10916 - Planetary Habitability and Stellar Activity.indd 1 28-05-18 3:09:33 PM 10916_9789813237421_tp.indd 2 19/6/18 1:28 PM Published by World Scientific Publishing Co. Pte. Ltd. 5 Toh Tuck Link, Singapore 596224 USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601 UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE Library of Congress Cataloging-in-Publication Data Names: Hanslmeier, Arnold, author. Title: Planetary habitability and stellar activity / Arnold Hanslmeier (University of Graz, Austria). Other titles: Advances in planetary science ; v. 3. Description: Singapore ; Hackensack, NJ : World Scientific, [2018] | Series: Advances in planetary science ; vol. 3 | Includes bibliographical references and index. Identifiers: LCCN 2018002459| ISBN 9789813237421 (hardcover ; alk. paper) | ISBN 9813237422 (hardcover ; alk. paper) Subjects: LCSH: Extrasolar planets. | Habitable planets. | Stellar activity. Classification: LCC QB820 .H363 2018 | DDC 523.2/4--dc23 LC record available at https://lccn.loc.gov/2018002459 British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. Copyright © 2018 by World Scientific Publishing Co. Pte. Ltd. All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the publisher. For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to photocopy is not required from the publisher. For any available supplementary material, please visit http://www.worldscientific.com/worldscibooks/10.1142/10916#t=suppl Desk Editor: Ng Kah Fee Typeset by Stallion Press Email: [email protected] Printed in Singapore KahFee - 10916 - Planetary Habitability and Stellar Activity.indd 2 28-05-18 3:09:33 PM June27,2018 18:19 PlanetaryHabitabilityandStellarActivity 9inx6in b3219-fm pagev Preface The first exoplanets were detected more than two decades ago. Since then, our knowledge about exoplanets has increased exponentially. Several thousandsoftheseobjectshavebeenidentified, andmanyparameterssuch as their sizes, masses, temperatures, distances to their host stars etc. have been confirmed. There are several reasons for this rapidly growing field of astrophysics. On the one hand, exoplanets can be detected with relatively small telescopes, only a precise photometry is required to detect their transits; on the other hand, several space missions have been devoted to increasingourknowledgeaboutthesestrangeworlds.However,thereisone open question: Could life exist elsewhere in the universe? In this book we mainly deal with the influence that host stars could have on exoplanets. In the first chapter, we give an overviewof the objects inour solarsystem. Tounderstandthe complexinteractionbetweenstellar activityandplanets,itisextremelyusefultostudytheseinteractionsonthe different planets and objects in the solar system. Some planets, like Earth or Jupiter, have magnetic fields that provide a shielding against charged energetic particles coming mainly from our host star the Sun. Others, like Mercury, only have weak protection and are very close to the Sun. In the second chapter, we give an overview on the Sun and its activity. Since the Sun is the only star where this activity can be studied and observed in detail, it is a proxy for stellar activity in general. Only in the case of the Sun can we observe processes during which huge amounts of energy are released (flares, CMEs) within a short time span and the propagationoftheseparticlesandradiationtotheplanetscanbemeasured almost in situ by space missions. The activity of the Sun is periodic, but v June27,2018 18:19 PlanetaryHabitabilityandStellarActivity 9inx6in b3219-fm pagevi vi Planetary Habitabilityand StellarActivity intermittent phases also exist during which solar activity is almost absent. We discuss all these aspects of space weather. In the third chapter, exoplanets are discussed. We briefly describe how exoplanets can be found and what types of exoplanets have been detected so far. Still, our detection methods are limited, and therefore the observed distribution of exoplanets is strongly biased because only large objects in the vicinity of their host stars can be detected easily. Stellar activity on a solar level is extremely hard to detect but, by comparing our Sun with other stars, we can understand how solar activity mighthavebeeninthepastandevolveinthefuture.Inthefourthchapter, stellaractivityisdiscussedandanoverviewonthebasicprinciplesofstellar structure and evolution is also provided. The main topic of the book is habitability and stellar activity. Several aspects of habitability are presented in Chapter 5. Since we know of only onesampleoflifeintheuniverse,lifeonEarth,wegivesomeargumentsthat lifeonexoplanetscouldevolveunderconditionssimilartotheconditionson Earthandsomesolarsystemobjects.Therefore,a habitablezonearounda starcanbedefinedastheregionwherewateronhypotheticalplanetscould exist in liquid form. Water seems to be the basic element for life. We will describewheresuchahabitablezonecanbeexpected(a)aroundastarand (b) around a giant planet. A galactic habitable zone also exists. Too close to the center of a galaxy and also too far life seems to be impossible. This is not a real strong limitation to the possible number of habitable planets around stars since a galaxy contains several 100 billions of stars and, even in the worstcase, if we arethe only habitable planet in our galaxy, billions of galaxies exist in the universe. So therefore, billions of habitable worlds could exist. In the last chapter, we again address to the question of the influence of stellar activity on planetary habitability. We will discuss in detail how the location of habitable zones around a star changes during stellar evolution. Within the next4 billionyears,the Sunwill progressivelyevolveinto a red giant and the Earth will become part of the Sun making it an extremely hostile hot environment for life. What would happen if a superflare on the Sun occurs? Could this be a threat to our highly evolved technological society? To answer such questions it is again useful to compare our Sun with other stars that are younger or older than the Sun. Each chapter of this books gives some introductory material for the interested reader and then actual literature is cited on the several topics. June27,2018 18:19 PlanetaryHabitabilityandStellarActivity 9inx6in b3219-fm pagevii Preface vii Using this literature, the reader can penetrate deeper into the actual research topics of this very rapidly evolving field. The author is very grateful to several colleagues who went through the manuscript and gave valuable suggestions and hints: Mag. Ines Juvan, Dr. Peter Leitner, Dr. Martin Leitzinger, Mag. Isabell Piantschitsch and Mrs. W. Isaacs for English editing. A. Hanslmeier b2530 International Strategic Relations and China’s National Security: World at the Crossroads TTTThhhhiiiissss ppppaaaaggggeeee iiiinnnntttteeeennnnttttiiiioooonnnnaaaallllllllyyyy lllleeeefffftttt bbbbllllaaaannnnkkkk b2530_FM.indd 6 01-Sep-16 11:03:06 AM June27,2018 18:19 PlanetaryHabitabilityandStellarActivity 9inx6in b3219-fm pageix Contents Preface v List of Figures xv List of Tables xxv 1. The Solar System 1 1.1 Objects of the solar system: An overview . . . . . . . . . 1 1.1.1 The planets . . . . . . . . . . . . . . . . . . . . . 1 1.1.2 Moons . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1.3 Dwarf planets . . . . . . . . . . . . . . . . . . . . 6 1.1.4 Asteroids and belts . . . . . . . . . . . . . . . . . 7 1.1.5 The heliosphere . . . . . . . . . . . . . . . . . . . 9 1.2 Physical parameters of planets . . . . . . . . . . . . . . . 10 1.2.1 Orbits . . . . . . . . . . . . . . . . . . . . . . . . 10 1.2.2 Mass . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.2.3 Size . . . . . . . . . . . . . . . . . . . . . . . . . 13 1.2.4 Rotation . . . . . . . . . . . . . . . . . . . . . . 14 1.2.5 Temperature . . . . . . . . . . . . . . . . . . . . 16 1.3 Planetary magnetic fields. . . . . . . . . . . . . . . . . . 19 1.3.1 Magnetic fields . . . . . . . . . . . . . . . . . . . 19 1.3.2 Geodynamo . . . . . . . . . . . . . . . . . . . . . 21 1.3.3 Shielding effects . . . . . . . . . . . . . . . . . . 25 1.4 The atmospheres of planets . . . . . . . . . . . . . . . . 26 1.4.1 Basic parameters describing an atmosphere . . . 26 1.4.2 Atmospheric escape . . . . . . . . . . . . . . . . 28 ix