Prologue _ Pluto is dead
01 What is a planet?
02 1000 Years of Planetary History
03 The moon is my enemy
04 The second best thing
05 Ice Nail
06 The End of the Solar System
07 It's raining = pouring
08 Lila, Intermission
09 The Tenth Planet
10 Stolen Stage
11 Planets or not
12 A very wicked person
13 Conflict and Discord

Epilogue _ Jupiter Moves

Acknowledgements
Translator's Note
Search

The discoverer of the tenth planet, 'once upon a time'
Astronomer Mike Brown, the only living person to have discovered a planet,
Why did he have to give up his honor and go down the path of the 'Pluto Killer'?

Pluto is dead

In August 2006, one of the most heated debates in modern astronomy took place in Prague, Czech Republic.
Although commonly known as the meeting of the International Astronomical Union (IAU) that decided the fate of Pluto, it was also the meeting that decided the definition of a planet and whether or not new planets would be added to the Solar System.
Pluto, which had enjoyed the status of the ninth planet in the solar system for 76 years since its discovery in 1930, was stripped of its status and demoted to a dwarf planet at this meeting.
The celestial body 'Eris', discovered in 2005, was 'briefly' called the tenth planet, but this meeting decided that its official status was 'dwarf planet'.

A proposal was made by American astronomers to increase the number of planets to 12, including Eris and Pluto, in an attempt to protect Pluto, the only planet discovered by an American. However, IAU meeting attendees voted to classify Pluto and Eris as "dwarf planets" and recognize only eight celestial bodies as planets.

Memoirs of the Pluto Killer

Voices of protest against the IAU's decision erupted here and there.
Even among astronomers, there were those who spoke out against it, some protesting that Pluto should be returned to its place, and some making threatening phone calls.
Letters from children dreaming of space followed, and a rally opposing Pluto's demotion was held in New Mexico, where Pluto's discoverer, Clyde Tombaugh, was a professor.
This outcry and criticism has been focused on one person in particular: Mike Brown, the astronomer who discovered Eris.

Mike Brown could have been credited with being the "discoverer of the tenth planet" and the "only living person to have discovered a planet," but he was dubbed the "Pluto Killer" for his insistence that Pluto and Eris should not be classified as planets, and for his discovery of Eris, which helped shape that decision.
This book is a memoir that records the whole story of this event through the process of him being the cause of Pluto's demotion of its planetary status, searching for a new celestial body, and contemplating the meaning of a planet.

A lonely hunter and astronomer still searching for new stars

In the world of astronomy, it is generally believed that all the important celestial bodies, such as planets, in the solar system have already been discovered, and that there are no more celestial bodies left to discover.
Automated, cutting-edge computers and massive telescopes have rapidly photographed the entire sky, creating a vast map that contains detailed records of the coordinates and brightness of almost every star, along with other physical quantities.
In this 21st century, Mike Brown is almost the only astronomer who is finding new celestial bodies.
Although everyone expected it to fail, Mike Brown began discovering new objects in 2002, and by 2003 had proven that many small objects similar in size to Pluto exist in the outermost regions of the solar system.
And in 2005, Eris, an object orbiting the Sun similar in size to Pluto, was discovered!
In "How I Killed Pluto," Mike Brown and his team persistently observe the universe, discover new celestial bodies, and verify and announce their findings.
When you discover a new celestial body through obsessive observation of astronomical images every night, the sense of accomplishment and joy is conveyed as it is, and when you see scientists worrying about whether someone will announce it first while verifying their findings before announcing them, you empathize with their worries and feel anxious along with them (in fact, while they were discovering and reviewing another dwarf planet, Haumea, a Spanish research team accessed the Brown team's observation records and announced it first).
Additionally, the book exudes the scientist's "scientific" wit, along with his "astronomical" love for his family, which is more important than the universe, and his collaboration with colleagues in optimal partnerships.
This book is a chronicle of Mike Brown's life as an astronomer and the controversy surrounding Pluto's demotion from planet status, but it is also filled with the process of persistent observation to find a 'new star,' the fierce debate in the astronomical community surrounding what a planet is, and human curiosity and passion for exploration toward the universe.