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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
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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
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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
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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.
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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
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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
