A vast and powerful space weather event has been observed at the solar system's innermost planet for the first time.
NASA's Messenger satellite, which has been in Mercurian orbit since 2011, detected what is known as a hot flow anomaly (HFA) emanating from the tiny world's bow shock. HFAs are common at Earth's bow shock and they have also been detected at Mars, Venus and Saturn, but to detect the phenomenon around Mercury is a space weather boon for scientists.
PHOTOS: Extreme Space Weather
"Planets have a bow shock the same way a supersonic jet does," said Vadim Uritsky at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "These hot flow anomalies are made of very hot solar wind deflected off the bow shock."
All the planets in the solar system are bathed in a constant flow of plasma carried by the million-mile-an-hour solar wind. As this stream of energized gas encounters a planet with a global magnetic field (in the case of Earth's magnetosphere) or a planet without a magnetic field (like Venus), the stream of particles flow around the immovable object like a stream of water flowing around a rock.