Tag Archives: space science

Planets & Stars

Planets: Ours and Others: From Earth to ExoplanetsPlanets: Ours and Others: From Earth to Exoplanets by Therese Encrenaz
My rating: 4 of 5 stars

The art of an insightful, timely, and scientifically rigorous overview is a difficult one. This is compounded when the subjects are as broad as planets and stars, respectively. Fortunately for the educated non-specialists, there two slender volumes succeed where many astronomy texts fail: they provide a comprehensive, up-to-date survey of two fields with enough breadth to be useful and accessible to the astronomy educator while retaining enough technical grit for those desiring more depth.

The first volume (Planets), by an atmospheric planetologist at the Paris Observatory, frames the current state of exoplanetary research and the search for life in the context of comparative planetology, starting with Earth and moving through our planetary system.

Beginning with a brief introduction to observing and exploring planets (including exoplanetary detection), Encrenaz moves into a description of theories of planetary formation and then on to the bulk of the book, treating the physical properties of planets. Using Earth as test case and exploring things like geological activity and the water cycle, she provides in-depth comparison of the atmospheres, compositions, and internal structures of the planets of our solar system, touching briefly on some outer-system moons as well.

All of this sets the stage for the final third of the book, a look at exoplanetary systems– their discovery, their properties, and a quick overview of the status of the search for life in the cosmos. The chapters here remind that this is not a book on exoplanets exclusively: rather, it’s a survey of what we know about planets, which any more must include a detailed exposition of the ways other planetary systems are informing this knowledge.

In some respects, this is more helpful than a book on exoplanets alone, allowing an understanding of our own planetary context in light of these new discoveries.

Birth, Evolution and Death of StarsBirth, Evolution and Death of Stars by James Lequeux
My rating: 4 of 5 stars

The second volume is a survey of the physical processes (including a fascinating and detailed analysis of the interstellar medium) governing the life of stars. Lequeux, also of the Paris Observatory, takes a slightly more technical approach. Indeed, it was at times difficult to follow his account of the complex processes taking place within a star at various points in its life cycle.

However, the technical aspects provide a conceptual rigor often glossed over in more popular texts. Topics covered include the birth, physics, evolution, and death of single stars as well as a chapter on the “zoo” of double stars. It concludes with a glimpse of the larger questions of galactic evolution that stellar life and death play into.

Perhaps most importantly, this account discusses the many open questions in stellar evolution, especially star death, and the importance of modeling stellar interiors.

Both books are slender, less than 200 pages each, and filled with diagrams, images, and (especially in Lequeux’s) equations. Both are translations of works originally published in French, and the awkward language at times bears witness to this though never actively detracting from the text.

Neither volume is a textbook (there are no problem sets, for instance), nor are they purely popularizations, maintaining a balance between general survey and in-depth technical treatment. Often I read a survey text and learn nothing new; in contrast, these works are introductions written by active experts in their respective fields, lifting the veil on the physics behind the concepts but keeping a wide and fairly accessible scope, filled with a wealth of new information.

This review first appeared in the September 2015 issue of The Planetarian.

Dwarf Planets and Asteroids: Minor Bodies of the Solar System

Dwarf Planets and Asteroids: Minor Bodies of the Solar SystemDwarf Planets and Asteroids: Minor Bodies of the Solar System by Thomas Wm. Hamilton
My rating: 3 of 5 stars

My first research project as an undergraduate was attempting to determine orbital parameters of some asteroids. I remember being fascinated by these obscure bodies and their mysterious classical names. If I had Dr. Hamilton’s slender volume at that time, some of my questions would have been answered.

The minor bodies of the solar system are an eclectic group with interesting histories, and Hamilton’s volume cracks the door onto this subject. The book (under 70 pages) gives a brief introduction to asteroids (nine pages), but is primarily a catalogue of information– physical characteristics, orbital data, and explanation of name and discovery– for select bodies. There is a lot of interesting information here, but unfortunately none of it is referenced. One example: according to Hamilton, asteroids 300 Geraldina was named by Auguste Charlois, an apparently prodigious asteroid-discoverer who was murdered by a former brother-in-law. There’s obviously a story here, but without references the reader is left with no avenue by which to learn more.

Worse yet is the omission of information related to the objects themselves. Dwarf planets are mentioned (and distinguished by bolding their names), but there is no discussion of their distinction from asteroids. Comets are mentioned without any explanation of how they differ from asteroids and dwarf planets and what this indicates about the physical nature of the solar system. The Yarkovsky Effect is mentioned three separate times without an explanation of what it is.

Finishing the book, I was left with far more questions than I had upon beginning it. Why do some asteroids discovered later have lower numbers than those discovered earlier (i.e., 6312 Robheinlein and 6470 Aldrin, for instance)? Why do some have names consisting of only numbers and letters (2012VP113, for example)? Is Quaoar officially considered a dwarf planet?

A simple response to these might be, “Look it up and find out,” but this leads to my major question regarding this book: in a day when I imagine information about all minor planets is available online somewhere (another reference that would have been helpful in this book), why publish a book with limited information about only a selection of asteroids? It might look on the observatory shelf, but as a catalogue it is inherently incomplete and immediately out of date.

This review first appeared in the September 2015 issue of The Planetarian.