A stellar performance

Astronomer Jay Pasachoff tells Martin Ince how dedication and his wide interests ensure that his popular textbooks are always exciting.

You may have thought you were quite adventurous, heading to Cornwall for that eclipse in August. If so, have a glance at Jay Pasachoff's website (www.williams.edu/astronomy/jay). It lists 29 eclipses he has seen, starting as a teenager in 1959 in the United States, and continuing from Finland to Papua New Guinea.

Pasachoff is no mere eclipse tourist. His research makes full use of the unique view an eclipse offers of the Sun's atmosphere, his scientific speciality. Satellites can view the solar atmosphere non-stop, but it takes their detectors about a second to produce an image. Viewing the August 11 eclipse from Romania, he used a ground-based telescope to record about 1,500 images: ten per second, fast enough to observe waves moving through it. He stresses that eclipses are not just a research tool for him but part of his mission in astronomy education. In Romania he was accompanied by a dozen students, at least two of whom will get undergraduate theses out of the results.

Pasachoff is most familiar in astronomy education as the author of two standard texts. Contemporary Astronomy has reached its fourth edition and Astronomy: From the Earth to the Universe its fifth. He explains that, although the books cover similar territory, they approach it very differently. As the title implies, Astronomy: From the Earth to the Universe takes a systematic approach in which the universe is viewed on a successively bigger scale, with the planets being dealt with before the stars. Contemporary Astronomy is designed for students taking perhaps only one semester of astronomy. It aims to grab their attention by bringing in new and spectacular material on stars and nebulae early on.

In addition, Pasachoff and a new co-author from the University of California at Berkeley, Alex Filippenko, are revising a one-semester text to appear in July 2000 as The Cosmos: Astronomy at the New Millennium , with the latest images from new satellites and ground-based telescopes in Hawaii, Chile and elsewhere. Pasachoff says that each of the books has been adopted by about 500 US universities: "There are usually 30 or so texts suitable for first-year astronomy but of these, three or four have about 80 per cent of the market." While the authors of the rival volumes are competitors, Pasachoff is quick to say that there is "camaraderie among authors, who know what we have all been through". The books he has produced have required "real dedication" and he regards them as the major achievement of his varied career. By contrast, some authors write a textbook "on the side," he says, "and it shows in the amount of detail they include and in major and minor inaccuracies". Writing in a fast-moving and complex science such as astronomy involves keeping abreast of discussions in many areas, which requires "constant devotion".

He thinks his wide interests outside science make him a better textbook author. At Williams College in upstate Massachusetts, where he is head of astronomy, only a minority of the students who take astronomy go on to major in it, or in astrophysics, also on offer. The rest (about 150 a year compared with about a dozen third and fourth-year astronomy majors) are in for a one-off encounter with the subject. So it helps to enliven their experience with material drawn from his interest in subjects such as art, rare books and theatre. His wife Naomi is now writing a book on dramatists, while Pasachoff has written a book on British artistic representations of comets and meteors with art historian Roberta J. M. Olson, and has written up his research on the solar corona in a high-level, co-authored book.

Williams College is a university that appears to offer much to aspiring textbook authors. It consistently appears among the top three "National Colleges" in ratings produced by US News and World Report . These are comparatively small universities that have a worthwhile research base but major in teaching, and that provide a more personal student experience than the big-city colleges.

Pasachoff listens to a wide range of influences, but insists that there is no substitute for the author's own judgement on what to include in a text. "An emphasis on exciting new material has always been part of the approach. I have always had material on black holes and quasars, and more recently on supernovae. There are now more chapters on cosmology and a separate one on the cosmic distance scale," the latter being an area of current controversy.

Even more striking than the changes from edition to edition in the subject matter Pasachoff covers is the altered expectation of the users about how rapidly it will be updated. Three years ago he started a website, on which there are updates and links based on even hotter material, such as new moons of Uranus, the loss of the Mars Climate Orbiter spacecraft and the first images from the new Chandra X-ray space telescope. The updates offer something relating to every chapter of Astronomy: From the Earth to the Universe and are clearly a massive labour. There is also a 32-page update to the book, which can be bought on its own or with it.

Pasachoff is also keen to spread the word that it is possible to look at the sky as well as read about it. The fifth edition of his Field Guide to the Stars and Planets is out this month. He describes it as a "trade book that is also used as a text for observational courses". In addition, he is involved with UK software house Maris, which employs mainly Russian experts and has developed the best-selling RedShift astronomy programme. RedShift2 can also be bought with Astronomy: From the Earth to the Universe , and there is a college edition, RedShift3, simplified but with some explanatory text, which will come with The Cosmos: Astronomy at the New Millennium . Pasachoff insists that any CD associated with one of his books has to maintain the same standard as the printed word. But he is no pedant and has an open and approachable style. As a rare-book aficionado, he "decided that books would be a good place to put the money received from books". With the guidance of the rare-book librarian at Williams College and a historian-of-science colleague at Harvard he has been buying first editions of books by Newton, Galileo and others. They are available in the college library for others to look at.

There is even interplanetary evidence of how well he is doing. "I have never been an expert on asteroids, but Ted Bowell [an asteroid astronomer in Arizona] was impressed enough by what I wrote about them to name one after me." Asteroid 5100 Pasachoff orbits the Sun in just under four years. Gesturing towards his wife and daughters, just out of earshot, he says:

"It's nice to think there is a Pasachoff up there to go with the more important ones down here."