Celestial Shadows - Sheehan, William

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Résumé :
Much of what is known about the universe came from the study of celestial shadows. This book looks in detail at the way eclipses and other celestial shadows have given us amazing insights into the nature of the objects in our solar system and how they are even helping us discover and analyze planets that orbit stars other than our Sun. A variety of eclipses, transits, and occultations of the mooons of Jupiter and Saturn, Pluto and its satellite Charon, asteroids and stars have helped astronomers to work out their dimensions, structures, and shapes - even the existence of atmospheres and structures of exoplanets. Long before Columbus set out to reach the Far East by sailing West, the curved shadow of the Earth on the Moon during a lunar eclipse revealed that we inhabit a round world, a globe. More recently, comparisons of the sunlit and Earthlit parts of the Moon have been used to determine changes in the Earth's brightness as a way of monitoring possible effects in cloud coverage which may be related to global warming. Shadows were used by the Greek mathematician Eratosthenes to work out the first estimate of the circumference of the Earth, by Galileo to measure the heights of the lunar mountains and by eighteenth century astronomers to determine the scale of the Solar System itself. Some of the rarest and most wonderful shadows of all are those cast onto Earth by the lovely Evening Star Venus as it goes between the Earth and the Sun. These majestic transits of Venus occur at most two in a century; after the 2012 transit, there is not a chance to observe this phenomenon until 2117, while the more common sweep of a total solar eclipse creates one of the most dramatic and awe-inspiring events of nature. Though it may have once been a source of consternation or dread, solar eclipses now lead thousands of amateur astronomers and eclipse-chasers to travel the globe in order to experience the dramatic view under totality. These phenomena are among the most spectacular available to observers and are given their full due in Westfall and Sheehan's comprehensive study.

Biographie:
William Sheehan has written many books on astronomy, including: Planets and Perception (1988), The Immortal Fire Within: the life and work of Edward Emerson Barnard (1995), The Planet Mars (1996), In Search of Planet Vulcan (with Richard Baum...

Sommaire:
Preface.- Part I. The Diversity of Eclipse Events.- Eclipse Phenomena.- The Waltz of the Planets.- The Performers.- Part II. A Transit Chronicle.- The Beginnings.- Scaling the Heavens.- A Century of Progress and Disappointment - and Completion.- Our Own Venus Transit - The June Flowers of 2004.- Part III. 2012 - Our Last Chance for a Venus Transit.- The 2012 Event.- Observing the 2012 Transit.- Mercury also Transits the Sun.- Transits Galore.- The Splendor of a Solar Eclipse.- The Beauty of a Lunar Eclipse.- Planetary Satellites.- Occultations - When Blocking the View is Helpful.- Appendices.- References.- Index.