XMM-Newton looking though Earth's magnetosheath
An illustration of ESA's XMM-Newton X-ray observatory looking through the magnetosheath, the outermost region of Earth's magnetosphere, which separates it from the solar wind – a flow of charged particles streaming from the Sun into interplanetary space. In this view, Earth is located on the left (beyond the edge of image) and the Sun towards the right.
XMM-Newton is an astrophysics observatory designed to study highly energetic phenomena across the cosmos, such as black holes and remnants of supernova explosions, which shine brightly in X-rays. The satellite follows a highly elliptical, 48-hour orbit around Earth.
While XMM-Newton's targets lie well beyond our planet, the line of sight of its X-ray imagers may sometimes pass through Earth's dayside magnetosheath, resulting in a diffuse soft X-ray emission in the foreground of the observation.
This emission is usually regarded as an unwanted contaminant by astrophysicists, but it provides an opportunity for plasma scientists, who have been analysing these data for many years, to investigate solar wind charge exchange events in the outer magnetosphere. These studies are now proving of value during preparations for the SMILE mission.