High energy astrophysics

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P1: Spk Trim: 246mm × 189mm Top: 10.193 mm Gutter: 18.98 mm
CUUK1326-FM CUUK1326-Longair 978 0 521 75618 1 August 13, 2010 2:27
xiv Preface
Much of the relevant historical material has been included in The Cosmic Century and
so that material will not be repeated here. I make references to the appropriate sections
of The Cosmic Century and other historical texts. I do this with considerable reluctance
since the historical development of high energy astrophysics has influenced strongly the
way in which the astrophysics has developed intellectually. History will not disappear
completely, but it will not be as prominent as in the earlier editions.
Much of the necessary material needed to obtain a modern view of galaxies and the large
scale structure of the Universe is included in Galaxy Formation. In particular, there is no
need to repeat much of the detailed discussion of galaxies and clusters, or the large scale
structure and dynamics of the Universe. These topics are, however, central to many of the
topics in this book and so summaries of the most important topics needed to understand
the astronomical context of high energy astrophysics are provided in Part I.
There was a strong emphasis upon the origin of cosmic rays in the first two editions. I
still consider this to be excellent material, particularly in the area of ultra-high energy
cosmic rays, but it has been somewhat abbreviated in the new edition.
There was also a considerable amount of material on detectors and telescopes in the
earlier edition. I believe this material is of the greatest interest and importance in understanding our ability of make observations in different wavebands. This aspect of the
subject has been strongly moderated in the new edition. These are fascinating topics, but
modern telescopes and detectors have become increasingly complex and sophisticated.
Summaries of a number of important topics in the physics of astronomical detectors and
telescopes are included as an appendix.
In the second edition, I devoted some space to high energy astrophysics in the Solar
System. This material has been abbreviated, but important topics such as the diffusion of
energetic charged particles in the Solar Wind and the acceleration of charged particles in
solar flares have been preserved.
The opportunity has been taken to rationalise the presentation of the physical and astrophysical processes so that duplication of material is avoided.
The writing has been very considerably tightened up so that the discussion is less discursive than in the earlier editions. Again, I regret the necessity of doing this since often
these asides provide valuable physical insights for reader new to the subject.
The aims of the present edition are the same as the earlier editions. A very wide range of
physical processes relevant for high energy astrophysics is discussed, the emphasis being
strongly upon the understanding of the underlying physics. I aim to maintain the informal
style of the earlier editions and have no hesitation about using the first person singular
or expressing my personal opinion about the material under discussion. The emphasis is
strongly upon physical principles and the discussion of general results rather than particular
models which may have only ephemeral appeal.
As I learned during the writing of The Cosmic Century, physics and astrophysics have
a symbiotic relation. On the one hand, the astrophysical sciences are concerned with the
application of the laws of physics to phenomena on a large scale in the Universe. On
the other hand, new laws of physics are discovered and tested through astronomical observations and their astrophysical interpretation. In these ways, the new astrophysics, of which

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