Table Of Contentasteroids
Kosmos
A series exploring our expanding knowledge
of the cosmos through science and technology
and investigating historical, contemporary
and future developments as well as providing
guidance for all those interested in astronomy.
Series Editor: Peter Morris
Already published:
Asteroids Clifford J. Cunningham
Jupiter William Sheehan and Thomas Hockey
Mars Stephen James O’Meara
Mercury William Sheehan
The Moon Bill Leatherbarrow
Saturn William Sheehan
The Sun Leon Golub and Jay M. Pasachoff
Asteroids
Clifford J. Cunningham
reaktion books
Published by Reaktion Books Ltd
Unit 32, Waterside
44–48 Wharf Road
London n1 7ux, uk
www.reaktionbooks.co.uk
First published 2021
Copyright © Clifford J. Cunningham 2021
All rights reserved
No part of this publication may be reproduced, stored in a retrieval system, or
transmitted, in any form or by any means, electronic, mechanical, photocopying,
recording or otherwise, without the prior permission of the publishers
Printer and bound in India by Replika Press Pvt. Ltd
A catalogue record for this book is available from the British Library
isbn 978 1 78914 358 4
contents
Foreword by Dr Gareth Williams 7
1 The Stranger Ceres 9
2 Where Are the Asteroids? 28
3 Explosions and Impacts 76
4 Asteroids in Popular Culture 114
5 Visiting an Asteroid 128
appendix: Engaging with Asteroids 156
Websites 171
References 175
Select Bibliography 181
Acknowledgements 183
Photo Acknowledgements 185
Index 187
Foreword
When I first became interested in asteroids, sometime in the
early 1970s, there was very little literature available on the
subject. Even among the professional community, there was little
interest in them. Research papers were few and far between, and
mentions in popular publications were practically non-existent.
Fast forward fifty years and asteroids are hot! We now know
that asteroids hit planets, sometimes catastrophically. Mankind
owes the fact that it is the dominant life-form on this planet to an
impact that wiped out the dinosaurs. Studies of the distribution of
the orbits and sizes of asteroids give us clues about the dynamics of
the early solar system and the effects of accretion versus collisions
as a process for forming objects. We have discovered objects in
locations that were unknown fifty years ago: some always closer
to the Sun than Earth; asteroids that revolve about the Sun in the
opposite direction to the major planets; objects that orbit entirely
beyond the orbit of Neptune; and celestial bodies whose appearance
lies somewhere between the star-like asteroids and the fuzziness
of comets. Amateur astronomers in the 1980s and early 1990s
were able to discover many new asteroids, but large professional
observing programmes, intended primarily to find the objects that
might hit us in the future, then swept up those that could be found
by amateurs. Many of them switched to observing light curves to
determine rotation periods and spin directions. Space probes have
7
asteroids
flown by or orbited more than a dozen asteroids, changing our view
of them from mere points of light in a telescope into worlds in their
own right. And more missions are planned.
I have been involved in tracking asteroids and comets
professionally for thirty years, with another ten years before that
as an amateur. Since 1990 I have seen the observational activity on
asteroids increase from roughly 50,000 observations a year to more
than 20 million. In 1990 we were tracking about 5,000 objects.
We now track almost a million. That has been a challenging data
management and computation problem.
Clifford Cunningham has written on asteroids for more than
thirty years, with a special interest in the history of asteroids. This
interest evolved into his PhD topic: a study of asteroids in England
in the early nineteenth century. His more scholarly publications
include a large number of volumes based on translations of
correspondences between numerous early nineteenth-century
astronomers on the topic of – you guessed it – asteroids.
Will this book tell you everything you need (or would want) to
know about asteroids? No, that is not possible in a book this size.
But it will hopefully whet your appetite to learn more. Enjoy.
Dr Gareth Williams, former Associate Director,
Minor Planet Center
8
one
The Stranger Ceres
Asteroids are quirky. Just consider the title of this chapter. It
comes from a chapter title of an 1877 book by William Oxley of
Manchester in the north of England. His book was as far removed
from science as it could possibly be. ‘Are you a stranger?’ asks
someone known as the Recorder. ‘I have lived on the planet Ceres,’
is the response. ‘I am not a departed Spirit, but am an inhabitant
of that planet you call Ceres.’1 The answer is so preposterous that
one can easily miss the two dramatic assumptions it contains: first,
the belief, widespread in the nineteenth century, that other celestial
bodies (including asteroids) can be inhabited; and second, that
Ceres is a planet.
The simple question ‘what are asteroids?’ has no simple answer.
Are they at least partly metallic objects orbiting the Sun between
Mars and Jupiter? Are they dead comets? Are they objects in the
outer solar system that were subject to weathering by liquid water?
Are they interstellar visitors? Are they companions of the planets,
following or leading the planets in the same orbits? Are they pristine
objects from the origin of the solar system? Asteroids are all these
things and more, making them the most interesting and diverse
diminutive objects in the solar system.
In essence asteroids are small objects, composed of silicates
or metal, that can be found throughout the solar system. Comets
are composed of silicates and ice. The major distinguishing factors
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