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The Local Bubble, or Local Cavity, is a relative cavity in the interstellar medium of the Orion Arm in the Milky Way. It contains the closest of celestial neighbours and among others, the Local Interstellar Cloud , the neighbouring G-Cloud, the Ursa Major Moving Group and the Hyades. It is at least 300 light years across, and is defined by its neutral-hydrogen density of about 0.05 atoms/cm, or approximately one tenth of the average for the ISM in the Milky Way , and one sixth that of the Local Interstellar Cloud.
The exceptionally sparse gas of the Local Bubble is the result of supernovae that exploded within the past ten to twenty million years. Geminga, a pulsar in the constellation Gemini, was once thought to be the remnant of a single supernova that created the Local Bubble, but now multiple supernovae in subgroup B1 of the Pleiades moving group are thought to have been responsible, becoming a remnant supershell.