The solar wind is diverted by Pluto, suggesting that, like some larger planets, the dwarf planet has a shield against the stream of energized particles emanating from the Sun.

Before NASA's New Horizons spacecraft visited the dwarf planet (pictured) in 2015, most scientists thought that Pluto interacted with the solar wind in the same way as a comet does. Comets lack protection from the wind, which diffuses around the cometary surface. But in analysing data from the spacecraft, David McComas at Princeton University in New Jersey and his colleagues identified a 'Plutopause' — a region where Pluto's tenuous atmosphere shields the dwarf planet from the solar wind.

The Plutopause is relatively small and well defined, much like the solar-wind boundaries around Mars and Venus. Even though Pluto is small, it still exerts enough gravitational pull to keep its atmosphere sufficiently close to provide a buffer from the solar wind.

J. Geophys. Res. Space Phys. http://doi.org/bgdv (2016)