Credit: Kislyakova et al. Nature Astronomy, 10.1038/s41550-024-02222-x, 2024
XMM-Newton X-ray image of the star 70 Ophiuchi (left) and the X-ray emission from the region ("Annulus") surrounding the star represented in a spectrum over the energy of the X-ray photons (right). Most of the emission consists of X-ray photons from the star itself but scattered within the observing telescope and across the camera (approximated by the model shown with the blue line), but there is a significant contribution around the oxygen K-alpha line at an energy of 0.56 keV that originates from the extended astrosphere rather than from the star (this contribution is included in the red model)