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
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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.
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