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  • Published: 15 July 2025
  • ISBN: 9781802064919
  • Imprint: Penguin Press
  • Format: Paperback
  • Pages: 288
  • RRP: $30.00

Alien Earths

Planet Hunting in the Cosmos





A superstar author chronicles our new age of exploration, discovering new worlds and describing how her team searches them for evidence of life

For thousands of years, humans have wondered whether we're alone in the cosmos. Now, for the first time, we have the technology to investigate. The question should have an obvious answer: yes or no. But once you try to find life elsewhere, you realize it is not so simple. How do you find it over cosmic distances? What actually is life?

As founding director of Cornell University's Carl Sagan Institute, astrophysicist Lisa Kaltenegger built a team of tenacious scientists from many disciplines to create a uniquely specialized toolkit to find life on faraway worlds. In Alien Earths, she demonstrates how we can use our homeworld as a Rosetta Stone, creatively analyzing Earth's history and its astonishing biosphere to inform this search. With infectious enthusiasm, she takes us on an eye-opening journey to the most unusual exoplanets that have shaken our worldview - planets covered in oceans of lava, lonely wanderers lost in space, and others with more than one sun in their sky! And the best contenders for Alien Earths. We also see the imagined worlds of science fiction and how close they come to reality.

We live in an incredible new epoch of exploration. As our witty and knowledgeable tour guide, Professor Kaltenegger shows how we discover not merely new continents, like the explorers of old, but whole new worlds circling other stars and how we could spot life there. Worlds from where aliens may even be gazing back at us. What if we're not alone?

  • Published: 15 July 2025
  • ISBN: 9781802064919
  • Imprint: Penguin Press
  • Format: Paperback
  • Pages: 288
  • RRP: $30.00

Praise for Alien Earths

Have dinosaurs evolved on other worlds? Could we spot a planet of glowing organisms? What nearby star systems are positioned to observe Earth passing in front of the sun? These are just a few of the questions that Lisa Kaltenegger has joyfully tackled. As the founding director of the Carl Sagan Institute at Cornell University, she has pioneered interdisciplinary work on the origins of life on Earth and the hunt for signs of life, or biosignatures, elsewhere in the universe. Alien Earths ... chronicles her insights and adventures spanning an idyllic childhood in Austria to her Cornell office, which previously belonged to the astronomer Carl Sagan

Becky Ferreira, New York Times

Lisa Kaltenegger is an enthusiastic guide to the search for life beyond our planet — and the new technologies that could help it succeed ... [the] director of Cornell’s Carl Sagan Institute, stands out from the crowd of authors as one of the world’s leading practitioners of astrobiology, with extensive personal involvement in the field. She writes with exemplary clarity about the remarkable diversity of the thousands of planets already identified beyond our solar system — and explains how we could detect clear signs of biology in outer space from the vast influx of data provided by a new generation of ultra-powerful telescopes over the next few years ... the tone of Alien Earths is overwhelmingly positive, as Kaltenegger rejoices in her "adventure to find life in the cosmos" and invites readers to share her excitement for the search, without getting carried away by "wild claims" with insufficient evidence ... she writes."The most exciting phase is about to begin."

Clive Cookson, Financial Times

Every other day we discover a new planet. How long before we find one that can sustain intelligent life? ... As Lisa Kaltenegger explains in her horizon-expanding new book, Alien Earths, this observation altered our perception of the universe ... And of course, if we can observe other planets, they can watch us

Rhys Blakely, The Times

E.T. is waiting to be found. And what's the best way to find life as we know it? Just ask Dr. Lisa Kaltenegger, the Director of the Carl Sagan Institute. She explains the latest methods (such as observing Earth from space to see what we can deduce about it), the power of the James Webb Telescope and the interdisciplinary team developing the tools we need to search for planets like our own.

Parade.com

an authoritative and enjoyable read

Andrew Robinson, Nature

a superb testament to the scientific virtue of curious wonder

Steven Poole, Wall Street Journal
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