Uranus and the outer planets

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dependence of dust production does not hold at all well for many short-period comets more than l AU from the Sun, for example, especially according to evidence from visual wavelength photometry. Ney's article constitutes a good review of pre-IRTF infrared astronomy while Campins and Hanner presage the approach that will be required for future interpretation of the best infrared observations. For more than a decade most of us have clung to Probstein's dusty gas dynamics. Wallis suggests the day is now here when we must move on to a more complete and realistic representation of the cometary coma and suggests the direction of March. Fechtig reviews the actual in situ measurements of interplanetary dust and discusses what parts of it appear to be cometary (>30%). Fraundorf, Brownlee, and Walker review laboratory studies of particles captured in the stratosphere and spherules collected from the ocean floor. The stratospheric "Brownlee particles" are widely thought to be at least in part cometary in origin. The first three papers in Part IV on the Coma deal with observations and their interpretation. Meisel and Morris review results of both old visual photometry and new photoelectric photometry and problems of comparing the two data sets. A'Hearn's review of optical spectrophotometry should be required reading for anyone doing photometry of comets. It is superb, as is Feldman on ultraviolet spectroscopy. The authors of all three observational papers are among the foremost practitioners in the fields whereof they write, and the expertise shows. Jackson writes on laboratory studies of spectroscopic parameters and rate constants used in the reduction of observations and the creation of theoretical models. His own laboratory work has been making needed results available for years. The final article in Part IV is by Huebner, Giguere, and Slattery on photochemical processes in the coma. Their team is one of the two active in detailed theoretical modeling of coma chemistry, and again the expertise shows. In Part V Brandt's article on plasma tails has great appeal to an observer, since he discusses observational results and offers reasonable sounding interpretations. Schmidt and Weymann give a nice presentation on their much less "visual" theoretical work on plasma flow around comets and almost convince me I really understand it. Russell, Luhmann, Elphic, and Neugebauer compare comets to Venus, because both have ionospheres and little or no intrinsic magnetic field, and review what we may expect of comets from their Venus experience. Ip and Axford consider a range of physical processes which may occur in cometary comae and ion tails, limiting them where possible from observations, and looking forward to the measurements that may tell us what situation really exists. Again all the authors in Part V are well known and experienced contributors to the field. Weissman opens Part VI with a discussion of the latest studies of the Oort Cloud, his own Monte Carlo

studies large among these. The Cloud has grown a bit, and its desriptions is becoming more precise, but its origin is still most uncertain. Everhart reviews the evolution of long- and short-period cometary orbits, work for which he is well known. Degewij and Tedesco consider the evidence for the evolution of comets into asteroids. Ponnamperuma and Ochiai conclude Part VI with a very sensible discussion of "Comets and Origin of Life," a topic which has occasionally generated much heat in recent years. The last conference which really covered the entire field of cometary research was held at Goddard Space Flight Center, October 28-November 1, 1974. The proceedings which followed in early 1976 included both reviews and contributions and were the most important single reference available until now. Even a cursory comparison shows the enormous observational advances that have occurred, particularly in ultraviolet and infrared spectroscopy and visual photometry. Laboratory work has continued on spectroscopic parameters and begun on dust samples that are almost surely cometary. Bigger and faster computers and better software have made their impact on coma chemistry, plasma studies, and in Monte Carlo studies of cometary orbital evolution. Persistent scientists have continued to coax new and important results out of very old data. In short, our field is a live, vital one that is represented exceedingly well by this new book in the University of Arizona Space Sciences Series. This book, like most of its series predecessors, is for now the best there is. Go out and buy a copy! RAY L. NEWBURN, JR. 1

Jet Propulsion Laboratory Pasadena, California 91109 Uranus and the Outer Planets. G. Hunt, ed. Cambridge Univ. Press, London/New York, 1982. ix + 307 pp., $34.50.

The IAU Colloquium No. 60 entitled "Uranus and the Outer Planets" was held at the University of Bath, England, during April 14-16, 1981 to celebrate the 200th anniversary of the discovery of the planet Uranus by William Herschel. This book contains all the invited papers but is more than simply a record of the meeting. It opens with Herschel's original paper on the discovery of Uranus (he thought it was a comet) reproduced from the Philosophical Transactions of the Royal Society. Then follow 70 pages devoted to the historical circumstances associated with the discovery and its impact on science, the public, and on Herschel This review was written in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

BOOK REVIEWS himself. Herschel was already a successful musician, with no formal training in the sciences, by the time he developed his interests in optics and astronomy. While pursuing a full-time career in music, he gradually cultivated these hobbies while educating himself in the sciences. But he was still an amateur when, at age 42, he discovered Uranus. The best telescopes he built were better than any others in existence. As a result of his discovery, Herschel received a pension from the Crown and became a full-time, professional astronomer. His life work in astronomy led to an entirely new view of the galaxy and universe, a fact not appreciated by his scientific contemporaries, who often could not verify his work owing to inferior instruments. It is unusual for a scientific colloquium to devote so much attention to historical background, but in this case it seems to be warranted by the particularly unusual and inspirational circumstances. The book cannot convey the experience of hearing Herschel's music played at the Guild Hall nor the experience of listening to the local "catch" quartet sing samples of songs sung primarily for the pleasure of the singers during Herschel's time. Nevertheless, readers will enjoy R. Porter's chapter describing the cultural and intellectual circles in Bath at the time Herschel lived there. This is followed by J. A. Bennett's absorbing account of Herschel's self-training, the events leading up to his discovery of Uranus, and the large impact that discovery had on both the astronomical and lay worlds. Then M. Hoskin summarizes Herschel's lifetime accomplishments in astronomy. In the following chapter, E. G. Forbes describes how Uranus was observed as a star on no fewer than 22 occasions between 1690 and 1771 before Herschel discovered it and recognized that it was not a star. In the final paper of the historical section, R. W. Smith describes the impact on astronomy of the discovery of Uranus--especially the research on and acceptance of the Titius-Bode law, the search for and discovery of Neptune, and the redirection of Herschel's career. The papers of the historical section are all interesting, concisely written, and well referenced for further reading. Their value will not be diminished by future discoveries concerning Uranus. The biggest section of the book, 166 pages, deals with the present knowledge of Uranus. The first two chapters deal with the origin and internal structure of Uranus. M. Podolak makes use of the planet's composition, inferred from observations and interior models, to judge cosmogonic theories of accretion and giant protoplanets. He favors the accretional theories but points out the need for considerable additional work before Uranus' origin is understood. An opposite line of reasoning is used by MacFarlane and Hubbard to update the interior models of Uranus. They use recent determination of D/H, J2, and rotational period to improve the models and apply cosmogonic considerations to deduce the internal composition, particularly the ice/rock ratio.

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W. I. Axford speculates on the magnetosphere of Uranus by first discussing the general theory of magnetospheres, then comparing the properties of known magnetospheres, and finally extrapolating to Uranus. The length of the chapter seems excessive in view of the paucity of information on any Uranian magnetosphere, but the interested reader will get a good qualitative idea of how magnetospheres are believed to form and what physical processes occur in them. Uranus' magnetosphere should be especially interesting because of the planet's large obliquity: solar wind particles may funnel directly into Uranus' sunward pole. The rotation of Uranus is concisely reviewed by R. M. Goody. He favors a period near 16 h deduced by most spectroscopic techniques, and from the values of J2 and oblateness of Uranus derived from occultation studies and the precession of the elliptical rings. I do not feel that this value is firmly established because several investigators, using various methods, derive a different value near 24 h. In particular, using the same method, instrument, and reduction technique, Hayes and Belton derived a period of 24 -+ 3 h, while Brown and Goody obtained 16.15 -+ 0.33 h. Moreover, "shepherding" satellites probably are responsible for some of the sharp edges, as well as for some of the precession of the rings. The latter fact has been ignored in derivations of J2. Furthermore, the oblateness refers to the occultation level, where seasonal and diurnal time constants for temperature changes are short. Thus this surface may bear little resemblance to the shape of an isobaric surface. A good and readable introductory review of current understanding of Uranus' atmospheric structure and composition is given by M. J. S. Belton. He also summarizes some unsolved problems and briefly speculates on their solutions. CCD images of Uranus and Neptune, as well as a photograph of Saturn's E ring and satellites taken with a coronagraph, are presented in a short chapter by B. A. Smith and H. J. Reitsema. Much better images are anticipated from Space Telescope and the Voyager 2 flyby of Uranus and Neptune. G. E. Hunt speculates on Uranus' meteorology by first discussing the meteorologies of Jupiter and Saturn and then pointing to the similarities and differences of the boundary conditions for Uranus. At the May 1982 COSPAR meeting in Ottawa, P. Gierash presented updated analyses of Voyager data indicating that Saturn's internal heat source is about the same fraction of the absorbed sunlight as Jupiter's. This would weaken? Hunt's argument that Saturn's stronger internal heat source is a factor in explaining Saturn's stronger zonal winds. However, Hunt's supporting argument is unaffected: Saturn's greater scale height increases the available potential energy for convective motion to drive the winds. This section concludes with an informative discus-

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sion of Uranus' satellites by D. Cruikshank and two enlightening papers (by Brahic and Elliot) on Uranus' rings. Cruikshank summarizes the unsatisfactory state of photometry and photovisual spectrophotometry, and the results from near-infrared spectrophotometry which point to H20 or other frosts on the satellite surfaces. He also discusses the satellites' probable masses and radii, and speculates on their origin. Brahic briefly discusses the discovery of the rings of Uranus and the deductions from these observations. The bulk of the chapter is devoted to a qualitative discussion of ring dynamics in general and in existing ring systems. Relevance to the origin of the solar system is pointed out. This is an important chapter for those wanting to achieve some understanding of the many physical phenomena observed in ring systems: resonances, horseshoe orbits, and guardian satellites. It is slower reading than the others, not because of the approach but because of the awkward English constructions which sporadically appear. Elliot concisely summarizes observations of Uranus' rings and the results deduced from these observations. He reports corrected values of the planet's radius and oblateness which supercede his original estimates, and concludes by discussing future prospects from occultations, Space Telescope, and Voyager. The third section of the book discusses expectations from future observations of Uranus using Space Telescope and the Voyager 2 flyby. J. Caldwell ably describes potential Uranus science from Space Telescope (to be launched in the first quarter of 1985), both in terms of the present complement of instruments and in terms of possible future additions. Prospects for the Voyager 2 encounter are outlined by E. C. Stone. The encounter will occur in January 1986 and is expected to reveal a wealth of information on the planet and its rings. Ifa magnetosphere exists, a "System III" rotational period may be obtained, in addition to a rotation period for the clouds. Selected pictures from the Saturn flyby are presented to give the reader an idea of what spatial resolution to expect at Uranus. The book concludes with a summary chapter by T. C. Owen and closing remarks by IAU General Secretary P. A. Wayman. Rather than reviewing the individual contributions, Owen emphasizes the several unique properties of the planet. These provide a fitting and thought-provoking conclusion to this volume. Although some 22 contributed papers are not included in this book, the volume provides the reader with a concise and well-rounded presentation of generally up-to-date results. This and the historical background helped to give me a good general appreciation of the Uranian system, and to awaken in me a heightened interest in, and anticipation of, the 1986 Voyager 2 flyby of Uranus. Voyager's initial results will be more meaningful to me as a consequence of having read this book. I recommend it to anyone who has

either a casual or serious interest in Herschel's planet. L. TRAFTON

Astronomy Department The University of Texas Austin, Texas 78712 Kosmicheslde issledovaniya. M. V. Keldysh and M. Ya. Marov. Nauka, Moscow, 1981. 1 ruble 80 kopecks. This book and its American counterpart (A Meeting with the Universe, edited by Bevan French and Steve Maran, NASA EP-177) currently occupy the ecological niche once held by Kepler's allegorical frontispiece to the Rudolphine Tables: a pretty picture with the implicit message to a powerful patron, "See what wonders we have accomplished with your generosity! May we, please, continue?" Although their formats differ (the American book is frankly done in coffeetable style, while the Russian one is normal size and has fewer color illustrations), both present a superficial account of space exploration in about 200 glossy pages, in a style that will not strain the brain of the average bureaucrat. Indeed, much of the text of the work reviewed here has been taken verbatim or with only minor editing from the pages of Pravda. (For an account addressed to the intelligent layman, see Marov's Planeti Solnechnoi Sistemy--in a ten-timeslarger edition on plain paper, for less than a third the price.) To quote from academician A. N. Tikhonov's preface, "The authors did not set themselves the goal of telling fully and at length about all the many aspects of studying and conquering space, knowing quite well that such a task could scarcely be completed. Furthermore, to overload it with individual details would obviously make the book less useful to readers not specifically devoted to space research to whom, above all, it is addressed." Like the French and Maran book, Space Research begins with a brief historical account of the origin of space exploration, followed by chapters on Earth satellites; the ionosphere, magnetosphere, and solar-terrestrial relations; and the Sun itself. Three chapters on planetary discoveries follow these in Keldysh and Marov, while the planetary chapter precedes the solar one in French and Maran. Then comes one on astrophysics, prominently featuring black holes, X-ray astronomy, and similarly trendy subjects. The next chapter in both books is on manned spaceflight, but then they diverge. Keldysh and Marov describe applications--communications satellites, "radio bridges through space on microwaves"; weather satellites; Earth-resource satellites with multiple spectral imaging channels; etc. They also empha-