The Argument for Pluto: Why the Tiny Dwarf Is Still a Planet

Last week, the release of Mike Brown's new book, How I Killed Pluto and Why It Had It Coming (we published an excerpt), sparked a heated debate among professionals and amateurs alike that we haven't seen since, well, Pluto was delisted as a planet several years ago. Leading the charge was Laurel Kornfeld, a freelance writer and community activist who has made a name for herself on the Internet as the Pluto savior.

Kornfeld, who holds degrees in journalism, Middle East studies and English education from both Rutgers and Harvard, is working on a book that argues why Pluto should still be considered our ninth planet. An excerpt is published below. She also maintains a blog about Pluto.

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And of all planets in our solar system, Pluto is the strangest, the most different, the most enigmatic, one of the furthest away, the least known, the smallest, and the most fascinating. Combine all of these with a natural sentiment favoring the underdog, and the result is public fascination with this tiny underdog planet that by all odds, should not even have been discovered when it was, much less endowed with the honor of designation as a planet.

New discoveries in the last decade have changed the planetary landscape to the point that Pluto is no longer the furthest planet, even in our own solar system, or the smallest. But it is still the boundary of an unknown, unexplored frontier. The solar system, it turns out, is bigger and more diverse than we ever imagined. Moons of planets have been imaged and shown to be entire worlds in their own right, worlds that may even harbor microbial life in subsurface oceans. Our own Moon has been found to have water. And instead of being a lonely outpost at the solar system's edge, Pluto is now the gateway to yet a new region beyond Neptune, the Kuiper Belt. It is the next planet to be explored by a robotic flyby mission, New Horizons, launched in January 2006 and scheduled to rendezvous with its target in July 2015.

All of the above result in Pluto being, to many, the most fascinating of the planets, a class of objects that have themselves long inspired awe and wonder in generations of people. Those who argue that opposition to its demotion is based on sentiment ignore the fact that from the beginning, sentiments such as awe, wonder, and curiosity were what first motivated our ancestors' attempts to make sense of the universe. Science can never be completely separated from sentiment on any side of any debate.

Tiny Pluto has inspired powerful sentiments among many, both supporters and opponents of its planetary status. That sentiment is just as strong among professional astronomers as it is among lay people. To many, the little world that should be a gateway to new planet discoveries was instead used to slam the door shut on any such discoveries. It is as though we saw a door open and wanted to go through it to find new wonders only to have that door shut in our faces by those who want to limit the solar system to a small, manageable number of planets. No wonder many people responded with bafflement and even anger. Who are this group of so-called elites that purport to dictate arbitrary limits on what can be considered a planet? Why should their view take precedence over all others if it is based more on interpretation of the facts than on the facts themselves?

Many who had hoped to settle the issue of Pluto's status at the International Astronomical Union (IAU) General Assembly in 2006 remain baffled by an ongoing, intense public reaction refusing to accept the IAU dictate. Like a refrain, they constantly question, why do people care so much about Pluto, a tiny, frozen world 3.6 billion miles from the Sun?

Originally coined by Dr. Alan Stern to refer to objects large enough to be in hydrostatic equilibrium but not large enough to gravitationally dominate their orbits, the term dwarf planet was never intended to mean these objects are not planets at all. The problem arose because of a continuing insistence that there can be only two types of planets -- terrestrial or rocky planets, and jovians or gas giants. Dwarf planets do not fit into either category. Thus, some astronomers arrived at the erroneous conclusion that they -- and anything not a terrestrial or jovian -- are not planets at all.

But why must there be only two types of planets? Why can there not be three, four, five, or even fifty types? Some supporters of the position that dwarf planets are not planets create a false dichotomy by pitting the large moons of the gas giants against the dwarf planets. How can objects like Pluto and Eris be considered planets yet larger objects like Ganymede and Titan not be considered planets, they ask.

Tiny Pluto has inspired powerful sentiments among many, both supporters and opponents of its planetary status.

Once again, Dr. Stern has a practical, reasonable proposal. Spherical moons of planets should be designated as satellite planets. His proposal is not new. The large moons of the gas giants were often referred to as secondary planets during the 19th century. Secondary planets are objects whose secondary orbit is around the Sun and primary orbit is around another planet as opposed to primary planets, which orbit the Sun directly.

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Nicholas Jackson is a former associate editor at The Atlantic.

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