Oplutonize: How Pluto gave the world a new word (3 photos)

In 2006, the English language acquired an unusual verb: "to pluto." The American Dialect Society even named it its "Word of the Year." The meaning is simple: to devalue or devalue something once considered important and meaningful.





Pluto's surface in natural color as seen by NASA's New Horizons spacecraft/ © NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Alex Parker

The verb, as you might have guessed, is directly related to one of the most significant events in modern astronomy—the reclassification of Pluto from a full-fledged planet to a dwarf planet.

Pluto was discovered on February 18, 1930, by 24-year-old American astronomer Clyde Tombaugh. At that time in history, humanity knew little about the structure of the Solar System, so the new discovery was almost immediately awarded the status of the ninth planet. Pluto held this title for over 76 years—until August 2006, when it was officially downgraded to a dwarf planet at the General Assembly of the International Astronomical Union (IAU).

Why was Pluto Plutonized?

It's a bit odd, but before 2006, the term "planet" was more historical than strictly scientific. Clarification was required after the discovery of numerous objects in the Kuiper Belt (near Pluto). This culminated in the discovery of Eris in 2005—an object that, based on the data obtained, appeared even larger than Pluto.

To avoid chaos (the Solar System could have acquired dozens of new planets), the IAU introduced a clear definition of a planet. To qualify for this status, an object must meet three criteria:

Orbit the Sun but not be a satellite. Pluto qualifies.

Have sufficient mass to be gravitationally shaped into a nearly spherical shape (hydrostatic equilibrium). Pluto qualifies.

Clear its orbital region of other objects of comparable size (be gravitationally dominant in its zone). Pluto qualifies.

Pluto's orbit passes through the Kuiper Belt, home to thousands of massive icy bodies. Pluto is one of many such objects, and it does not dominate this region.



Sunset on Pluto, captured by the New Horizons probe/ © NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Therefore, it was decided that objects that do not meet the last criterion will henceforth be classified as dwarf planets. There are currently five officially classified as dwarf planets: Ceres, Pluto, Eris, Haumea, and Makemake. Additionally, there are four more such objects that astronomers consider dwarf planets but have not yet received official recognition from the IAU: Sedna, Quaoar, Orcus, and Gungun.

There are at least four dozen other icy candidate objects in the Kuiper Belt, whose masses and sizes are still being refined. According to preliminary data, many of them are massive enough to be classified as dwarf planets. And there's no doubt that with the advent of new, powerful telescopes, the number of known dwarf planets will only grow.



The decision provoked (and continues to provoke) a strong reaction: from anger and disappointment to memes and jokes. It was in this storm that the verb "to pluto" was born, symbolizing the constant evolution of science. What seemed certain yesterday may be reconsidered tomorrow—and that's okay.

Pluto, of course, hasn't become smaller or worse off due to our manipulations—it remains the same distant, mysterious world at the edge of the solar system, with mountains, a thin atmosphere, five satellites, and likely even a subsurface ocean.