Investigating the Soft X-ray Background of the Milky Way

This thesis uses the data from twenty ROSAT and XMM observations to investigate the structures that generate the soft X-ray background of the Milky Way. Ten of these observations lie in the direction of the Loop 1 Superbubble, specifically, within the North Polar Spur, the Northern Bulge, and immediately south of the Galactic Plane. The others are located in the Anti-centre direction, where the X-ray background is less complex. Using a novel processing technique, point sources and enhancements were successively removed from the observations until only the Diffuse X-ray Background (DXRB) re¬mained. By modelling the spectra of this clean data, and separately analysing the 0 and 0 viii emission lines, the various structures in the DXRB were identified, and their properties determined. The resulting models strongly indicate the existence of three previously unidentified components: a 14 pc thick, 0.1 keV shell surrounding Loop I, an inhomogeneous 0.25 keV Galactic Halo, and a non-thermal component present in the Galactic Centre direction. In contrast with previous work, no evidence was found for a cool Galactic Halo. The centre of Loop I was placed 290 pc away, 80 pc farther than previously believed. Additionally, an ongoing interaction was discovered between the Local Hot Bubble and Loop I.