Local Bubble

The Local Bubble, or Local Cavity, is where we are in our galaxy. It is a relative cavity in the interstellar medium (ISM) of the Orion Arm in the Milky Way. It contains among others, the Local Interstellar Cloud, which contains the Solar System, and the G-Cloud. It is at least 300 light years across. It has a neutral-hydrogen density of about 0.05 atoms/cm3, or about one tenth of the average for the ISM in the Milky Way (0.5 atoms/cm3)
The exceptionally sparse gas of the Local Bubble is the result of supernovae that exploded within the past ten to twenty million years. The gas is still in an excited state, emitting in the X-ray band.