★★★★★ The Times, The Telegraph, and Financial Times Book of the Year 2024
★★★★★ Adam Grant, Malcolm Gladwell's "Next Big Idea Club" Must-Read

“Are we alone in the universe?”
There should be a clear 'yes' or 'no' answer to this question!

The ultimate planetary science book, exploring the cutting edge of extraterrestrial exploration—the search for "other Earths" and unknown life forms in the distant universe! For thousands of years, humanity has gazed up at the heavens, wondering if we are alone in the universe. But in the past, our means of finding the answer were limited.
But that's not the case now.
Today's advancements in science and technology are giving us a clear view of the deep universe, previously untouched by human sight and touch.
A planet covered in a magma ocean, a planet that survived the death and explosion of its star, a planet with four stars shining in the night sky... With the discovery of extraordinary planets continuing and the discovery of over 5,000 exoplanets in our cosmic backyard, we are on the verge of discovering the first potential Earth in the distant universe and encountering extraterrestrial life.

Lisa Kaltenegger, the author of this book and professor of astronomy at Cornell University, is a world-renowned astronomer who pioneered planetary modeling and light fingerprint research, deciphering cosmic light to track the environments and traces of life on exoplanets.
The light emitted from a planet leaves traces of its interactions with the planet's environment and life forms.
Luckily, we have a wonderful example of a planet where life thrives: Earth.
By comparing the light fingerprints of Earth and other planets, we can discover clues to life in other worlds.
Kaltenegger succeeded in making the existence of extraterrestrial life a 'verifiable target' by datafiguring out the light fingerprints of the Earth and other planets.
We are now standing on the threshold of discovering extraterrestrial life!

A planet's extensive biosphere is likely to transform it, much as it did on Earth.
For example, about 2 billion years ago, early life on Earth changed the atmosphere by releasing large amounts of oxygen as waste.
Based on this phenomenon, we can confirm the existence of life in the universe, and this method can be applied regardless of whether life wants to communicate with us or not.
--- From "Chapter 1: Message from the Pale Blue Dot"

About 4.5 billion years ago, something happened that is common in the universe, but very special to us.
A star and eight planets were created.
Billions of years later, life on the third planet orbiting this star gave it the name Sun.
4.5 billion is a huge number.
4.5 billion seconds is a little more than 142 years, which is much longer than the human lifespan.
4.5 billion years ago, the universe looked different than it does today.
In our galaxy, huge clouds composed mainly of hydrogen atoms and small amounts of gas, ice, and mineral grains rotate slowly in spiral arms.
The temperature was extremely cold, at minus 270 degrees Celsius, close to absolute zero.
The clouds moved slowly.
But the shock wave from a nearby exploding star caused a dramatic change.
It collapsed the cold clouds.
Then, as has happened countless times in the past in the universe, the materials that formed the clouds were attracted to each other by gravity, creating a hot, dense central mass.
This central material is a young star.
--- From "Chapter 2: The Small and Wonderful Home of the Universe"

This is an experience close to time travel.
A young Earth appears on my computer screen.
Volcanoes erupt, sending clouds of toxic gases into the atmosphere, the first oxygen molecules float through the air, the first thin ozone layer forms to protect the Earth's surface, and the first life forms emerge onto land, adding color to the planet.
Sunlight illuminates the Earth, illuminating a beautiful and ever-changing world.
Sunlight that reaches the Earth passes through the atmosphere and is re-emitted into space.
These lights contain images of Earth at the moment it departs for its journey into space.
The light leaving a planet leaves traces of its interactions with life and the environment.
In that respect, light provides a reference that can help us find other planets similar to Earth.
--- From "Chapter 3: The Time Passed by the Celestial Bodies of Life"

Astronomers alone cannot find life in the universe.
Astronomers draw valuable resources from colleagues in other departments, who sometimes find themselves at a loss as they try to figure out exactly what the astronomers want.
But thanks to a network of scientists and astronomy enthusiasts, some surprising and unique collaborations have emerged.
These collaborations will allow us to investigate the diverse life forms that inhabit the world and uncover their light fingerprints—their portraits in space—so we can identify life forms observed through telescopes.
--- From "Chapter 4: How to Find Life in Space"

Compared to water raindrops or snowflakes hitting our bodies, rock raindrops hitting our bodies is a natural disaster of a different dimension.
When a storm hits CoRoT-7 b, you'll need a tool that goes beyond an umbrella.
Douglas Adams' classic science fiction novel, The Hitchhiker's Guide to the Galaxy, offers this advice:
“It’s the perfect place to kite surf on lava, but avoid getting hit by the rock droplets.”
--- From "Chapter 5: Planets That Completely Deviated from Astronomers' Predictions"

I wondered whether life on a planet could survive the death of a star. Before the TESS space telescope discovered WD 1586 b, our research team modeled the exposed core of a dead star, investigating what kind of environment would form around it and using this to predict the distant future of the solar system.
As a result, it was discovered that the Goldilocks zone can persist for billions of years even around the corpse of a star.
That is, life can begin again.
Perhaps life could survive the ordeal of a star's death by hiding somewhere beneath the planet's surface.
--- From Chapter 6, “The Universe is Not a Distant Imagination”

Every point in space is at the center of the observable spherical universe, surrounded by the hot plasma of a young universe.
No matter where you are, whether on Earth or in a distant galaxy, you are at the center of the observable universe.
And all life, including aliens from somewhere in the distant past or future, is at the center of the observable universe.
We can therefore claim that we have regained our special human position as the center of the (observable) universe.

--- From "Chapter 7: At the Forefront of Cosmic Knowledge"