The identity crisis bedeviling Pluto continues unabated 10 years after the International Astronomical Union downgraded it to a dwarf planet. The question remains: Is Pluto a planet?

New evidence gathered by the New Horizons mission seems to suggest the answer might be, Yes, it is. Well, sort of.

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At the core of this new confusion is data from New Horizons showing Pluto's interaction with the solar wind is like nothing astronomers have seen ever before in our solar system. This would only be possible if Pluto were a planet in the generally accepted term of the IAU word.

 "The results are astonishing. We were fascinated and surprised," said David McComas, who manages the Solar Wind Around Pluto (SWAP) instrument aboard New Horizons and lead author of a study published in the Journal of Geophysical Research.

"We've now visited all nine of the classical planets and examined all their solar wind interactions, and we've never seen anything like this."

What this means is Pluto isn't a comet or a planet. It might also not be a dwarf planet.

Solar wind, a plasma ejected over 100 million miles per hour from the upper atmosphere of the sun, interacts differently with planets, comets and dwarf planets, according to astronomers. This powerful stream of charged particles is diverted when it hits a planet like Earth or Mars.

A comet will gently slow down the solar wind. But in Pluto's case, the result based on New Horizons data, is an "intermediate interaction." What this tells scientists is Pluto isn't a planet nor is it a comet, as was once thought. Pluto is a "hybrid."

"This is an intermediate interaction, a completely new type. It's not comet-like, and it's not planet-like. It's in-between," said Dr. David McComas, who manages the Solar Wind Around Pluto (SWAP) instrument aboard New Horizons.

McComas said SWAP measures the interaction between the solar wind and ions created by atmospheric loss from Pluto. These measurements provide a characterization of the total loss rate and allow scientists to examine the complex plasma interactions at Pluto for the first time

SWAP also discovered Pluto retained its heavy methane ions in its atmosphere, a finding that would not have been possible if Pluto were a comet. 

TagsPluto, planet, dwarf planet, International Astronomical Union, New Horizons, David McComas