Keele Research Repository

The Solar System is located within a low-density cavity known as the Local Bubble1–3, which appears to be filled with an X-ray-emitting gas at a temperature of 106 K (ref. 4). Such conditions are too harsh for typical interstellar atoms and molecules to survive2,3. The diffuse interstellar bands (DIBs), the carriers of which remain largely unidentified5, often appear as absorption features in stellar spectra6–8 and can be used to trace interstellar gas. Here we report the three-dimensional (3D) structure of the Local Bubble using two different DIB tracers (λ5,780 and λ5,797), which reveals that DIB carriers are present within the Bubble9–11. The 3D map shows low values of λ5,797/λ5,780 inside the Bubble compared with the outside. This finding proves that the carrier of the λ5,780 DIB can withstand X-ray photodissociation and sputtering by fast ions, whereas the carrier of the λ5,797 DIB succumbs. This implies that DIB carriers are more stable than hitherto thought, and that the carrier of the λ5,780 DIB must be larger than that of the λ5,797 DIB12. Alternatively, small-scale denser (and cooler) structures that shield some of the DIB carriers must be prevalent within the Bubble, suggesting that such structures may be an intrinsic feature of supernova-driven bubbles.