Up until recently there has not been a really good treatment of photometry.
Fortunately, Shepard has rectified this with his Introduction to Planetary Photometry
in 2017. I have retained a section on this subject for practical reasons, but Shepard’s
book should be consulted for detailed definitions and derivations. In the field of
spectroscopy and non-local thermal equilibrium processes, I have found Non-LTE
Radiative Transfer in the Atmosphere by Lopez-Puertas and Taylor to be very
useful.
Hans Rickman completed a book on The Origin and Evolution of Comets Ten
Years after the Nice Model and One Year after Rosetta at the end of 2017 where the
emphasis is on the origin and dynamics of comets with respect to Solar System
evolution models. We will touch briefly on this subject here, but readers are referred
to Rickman’s text for greater detail.
It is with the relative absence of good introductory texts on comets in mind that
the concept for this book has been developed while simultaneously discussing new
information acquired at the Rosetta target comet. It is intended as a companion for an
introductory course on cometary physics at master’s level. Obviously, this drives
certain decisions about content, and inevitably, I cannot reference every work about
comets. This is all the more clear when you look in the ADS abstracting service and
discover that between 2014 and 2019 alone, there were more than 4800 entries with
the work “comet” in the title with over 1400 of them being refereed. As a consequence of this, I have tended to refer only briefly to certain types of object
(e.g. sun-grazing comets for which Jones et al. (2018) have written a review) and
limited discussions of the plasma environment (which has been covered recently in a
review by Gombosi (2014)). Several authors have been rigorous in deriving important equations within their texts. (Both Cravens and Gombosi have done this
extremely well, for example.) Here, derivations are limited often simply to reduce
the time and space necessary to develop them. But it should be emphasized that
without study of the mathematical detail, understanding can only be limited. Hence,
students are encouraged to search out the more mathematical treatments to flesh out
what is written here and references have been given where appropriate. Furthermore,
this work is not intended as a comprehensive review. Reviewing 5000+ papers
would be ludicrous and the reference list would end up being around 150 pages
alone. However, I have tried to work with papers that are informative on the key
topics. I apologize in advance if your particular favourite has not been tagged.
The text is divided into five main sections. We begin by looking at orbital
dynamics and classification. In the next sections, we look at the nucleus, the gas
distribution and composition, the dust emission, and the plasma interactions. This
seems to be a natural way to divide the subject to provide structure, but the reader
should be aware, even at this point, that treating one aspect in isolation is not a viable
approach to the study of these complex objects, and it is the purpose of this book to
provide sufficient background in all aspects of cometary research such that links
between phenomena can be appreciated. I have included three smaller chapters at the
end on related topics.
Since the first far spacecraft encounter with 21P/Giacobini-Zinner by NASA’s
ISEE-3 spacecraft in 1985, there have been numerous fly-bys of comets that have
brought us a vast amount of new information (Table 1). Here, though, we do draw
xii
Preface (Motivation and Scope)
Fortunately, Shepard has rectified this with his Introduction to Planetary Photometry
in 2017. I have retained a section on this subject for practical reasons, but Shepard’s
book should be consulted for detailed definitions and derivations. In the field of
spectroscopy and non-local thermal equilibrium processes, I have found Non-LTE
Radiative Transfer in the Atmosphere by Lopez-Puertas and Taylor to be very
useful.
Hans Rickman completed a book on The Origin and Evolution of Comets Ten
Years after the Nice Model and One Year after Rosetta at the end of 2017 where the
emphasis is on the origin and dynamics of comets with respect to Solar System
evolution models. We will touch briefly on this subject here, but readers are referred
to Rickman’s text for greater detail.
It is with the relative absence of good introductory texts on comets in mind that
the concept for this book has been developed while simultaneously discussing new
information acquired at the Rosetta target comet. It is intended as a companion for an
introductory course on cometary physics at master’s level. Obviously, this drives
certain decisions about content, and inevitably, I cannot reference every work about
comets. This is all the more clear when you look in the ADS abstracting service and
discover that between 2014 and 2019 alone, there were more than 4800 entries with
the work “comet” in the title with over 1400 of them being refereed. As a consequence of this, I have tended to refer only briefly to certain types of object
(e.g. sun-grazing comets for which Jones et al. (2018) have written a review) and
limited discussions of the plasma environment (which has been covered recently in a
review by Gombosi (2014)). Several authors have been rigorous in deriving important equations within their texts. (Both Cravens and Gombosi have done this
extremely well, for example.) Here, derivations are limited often simply to reduce
the time and space necessary to develop them. But it should be emphasized that
without study of the mathematical detail, understanding can only be limited. Hence,
students are encouraged to search out the more mathematical treatments to flesh out
what is written here and references have been given where appropriate. Furthermore,
this work is not intended as a comprehensive review. Reviewing 5000+ papers
would be ludicrous and the reference list would end up being around 150 pages
alone. However, I have tried to work with papers that are informative on the key
topics. I apologize in advance if your particular favourite has not been tagged.
The text is divided into five main sections. We begin by looking at orbital
dynamics and classification. In the next sections, we look at the nucleus, the gas
distribution and composition, the dust emission, and the plasma interactions. This
seems to be a natural way to divide the subject to provide structure, but the reader
should be aware, even at this point, that treating one aspect in isolation is not a viable
approach to the study of these complex objects, and it is the purpose of this book to
provide sufficient background in all aspects of cometary research such that links
between phenomena can be appreciated. I have included three smaller chapters at the
end on related topics.
Since the first far spacecraft encounter with 21P/Giacobini-Zinner by NASA’s
ISEE-3 spacecraft in 1985, there have been numerous fly-bys of comets that have
brought us a vast amount of new information (Table 1). Here, though, we do draw
xii
Preface (Motivation and Scope)