André Brahic is an astrophysicist. Besides teaching at Paris-VII University, he heads the research group on gamma-gravitation at the Atomic Energy Commission, at Saclay. He is credited, with William Hubbard, with the discovery of the rings of Neptune in 1984. He is the author of the highly successful Enfants du Soleil and Lumières d’étoiles. Les couleurs de l’invisible.
Bradford Smith, a specialist in solar system cosmogony and stellar astronomy, is affiliated with the Institute for Astronomy at the University of Hawaii.

Is there extra-terrestrial life? And if there is, is it necessarily intelligent life?
Although the idea of extra-terrestrial life was for a long time relegated to the realm of science fiction, some scientists think that the discovery of an advanced alien civilisation could occur during the course of the 21st century. Astrophysicists have started to detect possible life-sustaining territories near our own planet. A discovery of this nature would be a major turning point in the history of humankind — with enormous practical, sociological and philosophical consequences. For human beings, it would constitute the most significant event since their appearance on the planet Earth.

• The birth of a new scientific discipline, known as exobiology.
• A review of the latest scientific findings, which indicate that the discovery of an advanced alien civilisation could occur sometime during the present century.
• A brilliant, enthusiastic and accessible work by two of the greatest living astronomers.
• The book is illustrated with many previously unpublished photographs.