The Solar System in Close-Up Read online

  Astronomers' Universe

  Series Editor

  Martin BeechCampion College, The Univ of Regina, Regina, Saskatchewan, Canada

  More information about this series at http://​www.​springer.​com/​series/​6960

  John Wilkinson

  The Solar System in Close-Up

  John WilkinsonCastlemaine, Victoria, Australia

  ISSN 1614-659Xe-ISSN 2197-6651

  ISBN 978-3-319-27627-4e-ISBN 978-3-319-27629-8

  DOI 10.1007/978-3-319-27629-8

  Library of Congress Control Number: 2016934072

  © Springer International Publishing Switzerland 2016

  Astronomers’ Universe

  This Springer imprint is published by Springer Nature

  This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed.

  The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.

  The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or thex editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made.

  Cover illustration: Artistic impression of the New Horizon’s probe approaching Pluto in July 2015.

  Image credit: NASA/JHU APL/SwRI/Steve Gribben.

  Printed on acid-free paper

  The registered company is Springer International Publishing AG Switzerland

  Preface

  The overwhelming importance of the solar system lies in the fact that we are part of it; its origin and evolution are part of our own history. Astronomers have traditionally observed the solar system for the past few centuries via optical telescopes from the Earth’s surface. Then in 1957, a new method of exploration began with the launch of the first artificial satellite—this event marked the beginning of the Space Age. Since this time, humans have improved the technology of their spacecraft to the point where they can now send probes deep into the solar system to places never seen before. In the past few decades, there have been many space probes sent to explore the crater-strewn surface of Mercury and the roasting hot surface of Venus. In 1969, the first humans walked on the surface of the Moon. Since then, we have placed several robotic probes on the surface of Mars and used them to search for life on this planet. The giant planets Jupiter and Saturn together with their many moons and ring systems have also undergone extensive up-close exploration by space probes such as Voyager and Cassini. Saturn’s rings are arguably the most spectacular structure in the solar system, and if placed from end to end, they would reach from Earth to the Moon. The cold icy planets of Uranus and Neptune have thin ring systems and more moons than previously thought.

  In 2011–2012, the Dawn spacecraft explored the asteroid Vesta before moving on to the largest asteroid Ceres in 2015. In 2014, another spacecraft called Rosetta landed a probe on the surface of a comet—a momentous occasion. And in 2015, the New Horizons spacecraft visited Pluto and provided a wealth of new information about this dwarf planet and its system of five moons.

  During the past decade, astronomers have used the Hubble Space Telescope to discover other planet-like bodies orbiting beyond Neptune and Pluto, in far-out regions of the solar system called the Kuiper belt and Oort cloud. These new discoveries have provided astronomers with new insights into the origins of the solar system.

  These new explorations have revealed that Earth’s planetary neighbours are fascinating worlds. Today, we stand on the threshold of the next phase of planetary exploration. Many new missions are currently under way and many more are being planned.

  This book explores recent advances in our understanding of the solar system, in particular the effect on this understanding that the most recent spacecraft missions and the Hubble Space Telescope have provided. This book is, therefore, a record of the many discoveries made about the solar system in recent years using the context of space technology.

  John Wilkinson

  Acknowledgements

  The author and publisher are grateful to the following for the use of photographs in this publication. National Aeronautics and Space Administration (NASA),

  European Space Agency (ESA),

  Hubble Space Telescope (HST),

  European Southern Observatory (ESO),

  Keck Observatory,

  John Wilkinson (author).

  While every care has been taken to trace and acknowledge copyright, the author apologises in advance for any accidental infringement where copyright has proved untraceable. He will be pleased to come to a suitable arrangement with the rightful owner in each case.

  Notes: The websites used in this book were correct at the time of writing.

  Contents

  1 The New Solar System

  Introduction

  Discovering New Planets

  What Is a Planet?​

  Difference Between a Planet and Dwarf Planet

  Moons and Dwarf Planets

  Features of the Solar System

  Formation of the Solar System

  The Asteroid Belt

  The Kuiper Belt

  The Oort Cloud

  Comets

  The Modern Nebula Theory

  The Modern Laplacian Theory

  The Nice Model

  The Grand Tack Hypothesis

  In Conclusion

  Further Information

  2 Space Probes and Telescopes

  Space Telescopes

  The Hubble Space Telescope

  The Chandra Space Telescope

  The XXM-Newton Space Telescope

  The Spitzer Space Telescope

  The Kepler Space Telescope

  Future Space Telescopes

  Using Space Probes to Explore the Solar System

  Current Probes in the Solar System

  The Messenger Probe

  The New Horizons Probe

  The Stereo Probe

  The Rosetta Probe

  The Dawn Probe

  Solar Dynamics Observatory

  The Juno Probe

  Mars Science Laboratory

  Probing Comets

  Probes Leaving the Solar System

  Further Information

  3 The Dominant Sun

  Probing the Sun

  Features of the Sun

  Energy and Luminosity

  Zones of the Sun

  The Core of the Sun

  The Radiative Zone

  The Convective Zone

  The Photosphere

  The Chromosphere

  The Corona

  The Solar Wind

  Cycles in Solar Activity

  Types of Radiation from the Sun

  Solar Eclipses

  Influence of the Sun on Earth

  The Sun’s Future

  Further Information

  4 Mercury:​ The Iron Planet

  Early Views About Mercury

  Probing Mercury

  Position and Orbit

  Density and Composition

  The Surface

  Mercury’s Atmosphere

&nb
sp; Temperature and Seasons

  Magnetic Field

  Further Information

  5 Venus:​ A Hot, Toxic Planet

  Early Views About Venus

  Probing Venus

  Position and Orbit

  Density and Composition

  The Surface

  The Atmosphere

  Temperature and Seasons

  Magnetic Field

  Further Information

  6 Earth:​ The Planet of Life

  Early Views About Earth

  Probing Earth

  Position and Orbit

  Density and Composition

  The Surface

  The Atmosphere

  Temperature and Seasons

  Magnetic Field

  The Moon

  Early Views About the Moon

  Probing the Moon

  Position and Orbit

  Density and Composition

  The Surface

  The Atmosphere of the Moon

  Temperature

  Magnetic Field

  Further Information

  7 Mars:​ The Red Planet

  Early Views About Mars

  Probing Mars

  Position and Orbit

  Density and Composition

  The Surface

  The Martian Atmosphere

  Temperature and Seasons

  Magnetic Field

  Martian Moons

  Further Information

  8 The Asteroid Belt

  Early Views About the Asteroids

  Probing the Asteroids

  Position and Orbit

  Asteroid Collisions with Earth

  Size and Composition

  The Surface

  The Atmosphere

  Temperature

  Magnetic Field

  Further Information

  9 Jupiter:​ The Gas Giant

  Early Views About Jupiter

  Probing Jupiter

  Position and Orbit

  Density and Composition

  The Surface

  The Atmosphere

  Jupiter’s Ring System

  Temperature and Seasons

  Magnetic Field

  Moons of Jupiter

  Other Moons of Jupiter

  Further Information

  10 Saturn:​ The Ringed Planet

  Early Views About Saturn

  Probing Saturn

  Position and Orbit

  Density and Composition

  The Surface

  The Atmosphere

  The Rings

  Temperature and Seasons

  Magnetic Field

  Moons of Saturn

  Other Moons of Saturn

  Chariklo

  Further Information

  11 Uranus:​ The Coldest Planet

  Early Views About Uranus

  Probing Uranus

  Position and Orbit

  Density and Composition

  The Surface

  The Atmosphere

  The Rings

  Temperature and Seasons

  Magnetic Field

  Moons

  Further Information

  12 Neptune:​ Another Cold World

  Early Views About Neptune

  Probing Neptune

  Position and Orbit

  Density and Composition

  The Surface

  The Atmosphere

  The Rings

  Temperature and Seasons

  Magnetic Field

  Moons of Neptune

  Neptune’s Status in the Solar System

  Further Information

  13 Beyond Neptune:​ TNO’s and Comets

  The Kuiper Belt

  Pluto

  Early Views About Pluto

  Probing Pluto

  Position and Orbit

  Density and Composition

  The Surface

  The Atmosphere

  Temperature and Seasons

  Magnetic Field

  Moons of Pluto

  Other Kuiper Belt Objects

  The Scattered Disc

  The Oort Cloud

  Comets

  Parts of a Comet

  Probing Comets

  Meteoroids

  The Future

  Further Information

  Glossary

  About the Author

  Index

  © Springer International Publishing Switzerland 2016

  John WilkinsonThe Solar System in Close-UpAstronomers' Universe10.1007/978-3-319-27629-8_1

  1. The New Solar System

  John Wilkinson1

  (1)Castlemaine, Victoria, Australia

  Highlights

  Latest definition of what constitutes a planet and dwarf planet.

  Mathematics can be used to distinguish between a planet and dwarf planet.

  Hubble discovers the first proto-planetary discs around young stars.

  The Modern Laplacian theory has been successful at making key predictions about the physical and chemical structure of the solar system.

  The Nice model and the Grand Tack hypothesis provide new ideas about the evolution of the solar system.

  Introduction

  For thousands of years, the movement of the stars and planets across the night sky has fascinated humans. Humans have wondered what these objects are made of, how they move across the sky, and whether these worlds contain other living beings like us.

  In ancient times people noted the position of the Sun in the various seasons and its effect on crop growth. They also knew how the Moon affected the tides. And they observed objects called planets moving against a background of stars. The Babylonians even developed a calendar based on the movement of the planets visible to the unaided eye. In fact, the names of the days of our week originate from the Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn. These objects are the classical objects of our night sky.

  The word ‘planet’ comes from the Greek word meaning ‘wanderers’. The Greeks observed that the planets wandered against a background of stars that remained relatively fixed in relation to each other. The band across the sky through which the planets moved was called the zodiac. The star groups or constellations that form the zodiac were given names of animals, for example, the constellation Leo resembled a lion, and Taurus resembled a bull.

  Early Western and Arab civilisations and the ancient Greeks believed that the Earth was at the centre of the universe with the Sun, Moon and the then known planets orbiting around it. This view was challenged by Polish astronomer Nicolaus Copernicus in the sixteenth century when he suggested that all the planets, including the Earth, orbited the Sun in near circular orbits. By using a Sun-centered model, Copernicus was able to determine which planets were closer to the Sun than the Earth and which were further away. Because Mercury and Venus were always close to the Sun, Copernicus concluded that their orbits must lie inside that of the Earth. The other planets known at that time, Mars, Jupiter and Saturn, were often seen high in the night sky, far away from the Sun, so Copernicus concluded that their orbits must lie outside the Earth’s orbit.

  It was not until early in the seventeenth century that the German, Johannes Kepler showed that the orbits of the planets around the Sun were elliptical, rather than circular. Kepler also showed that a planet moved faster when closer to the Sun and slower when further from the Sun, and he developed a mathematical relationship between the planet’s distance from the Sun and the length of time it takes to orbit the Sun once. These three proven observations became known as Kepler’s Laws of planetary motion.