Four images from New Horizons’ Long Range Reconnaissance Imager (LORRI) were combined with color data from the Ralph instrument to create this global view of Pluto. The images, taken when the spacecraft was 280,000 miles (450,000 kilometers) away from Pluto, show features as small as 1.4 miles (2.2 kilometers).

(NASA/JHUAPL/SwRI)

Even after officially demoting it to a dwarf planet, researchers still aren’t quite sure what to make of Pluto. A recently published study makes categorizing the former planet even more difficult.

In a study published in the Journal of Geophysical Research last week, space physicists revealed that Pluto behaves less like a comet and more like a planet based on the way it interacts with solar wind.

Solar wind is the plasma that is expelled from the sun into the solar system at a rate of 100 million miles per hour. It bathes planets, asteroids, comets and interplanetary space with protons and electrons.

Before this discovery, most researchers believed that Pluto was characterized more like a comet, which has a large region of gentle slowing of the solar wind, as opposed to the abrupt diversion solar wind encounters on planets like Mars or Venus, according to NASA. They’ve found out that Pluto is a hybrid.

“This is a type of interaction we’ve never seen before anywhere in our solar system,” said lead author David J. McComas. “The results are astonishing.”

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Because Pluto is the farthest from the sun at a distance averaging about 3.7 billion miles, and because it’s the smallest, researchers believed its gravity would not be strong enough to hold onto heavy ions in its extended atmosphere, according to NASA. However, “Pluto’s gravity clearly is enough to keep material relatively confined,” said McComas.

Researchers also found that, like Earth, Pluto has a long ion tail that extends downward by at least a distance of about 738,000 miles and is loaded with heavy ions from the atmosphere. It also has “considerable structure,” they said.

The dwarf planet’s obstruction of the solar wind upwind of the planet is smaller than previously believed, also according to NASA. The wind isn’t blocked until about the distance of a couple planetary radii, or 1,844 miles - about the distance between Chicago and Los Angeles. Pluto also has a very thin boundary of its tail of heavy ions and the sheath of shocked solar wind that presents an obstacle to its flow.

“Comparing the solar wind-Pluto interaction to the solar wind-interaction for other planets and bodies is interesting because the physical conditions are different for each, and the dominant physical processes depend on those conditions,” said co-author Heather Elliott.

“These results speak to the power of exploration,” said New Horizons principal investigator Alan Stern. “Once again we’ve gone to a new kind of place and found ourselves discovering entirely new kinds of expressions in nature.”

MORE ON WEATHER.COM: New Horizons Pluto Images

New Horizons scientists made this false-color image of Pluto using a technique called principal component analysis to highlight the many subtle color differences between Pluto's distinct regions. The image data were collected by the spacecraft’s Ralph/MVIC color camera on July 14 at 11:11 AM UTC, from a range of 22,000 miles (35,000 kilometers). (Credits:NASA/JHUAPL/SwRI)