Local Bubble


Following Fruhn: http://www.daviddarling.info/encyclopedia/L/Local_Bubble.html

The Local Bubble is a great cavity in the interstellar medium (ISM), at least 300 light-years across, within which the Sun and many nearby stars reside. The Local Bubble has a neutral hydrogen density of only about 0.07 atoms per cubic centimeter – at least 10 times lower than the average ISM in the Galaxy – and also contains a thin gruel of million-degree X-ray-emitting plasma. These observations have led astronomers to conclude that the Bubble was formed between a few hundred thousand and a few million years ago by several relatively nearby supernova explosions that pushed aside gas and dust in the ISM leaving the current depleted expanse of hot, low density material.