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Local Bubble

Cavity in the interstellar medium which contains the Local Interstellar Cloud

The Local Bubble, or Local Cavity, is a relative cavity in the interstellar medium (ISM) of the Orion Arm in the Milky Way. It contains the nearest stars and brown dwarfs and, among others, the Local Interstellar Cloud (which contains the Solar System), the neighboring G-Cloud, the Ursa Major moving group (List of nearby stellar associations and moving groups stellar moving group), and the Hyades (the nearest open cluster). It is estimated to be at least 1000 light years in size, and is defined by its neutral-hydrogen density of about 0.05 atoms/cm3, or approximately one tenth of the average for the ISM in the Milky Way (0.5 atoms/cm3), and one sixth that of the Local Interstellar Cloud (0.3 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. 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. Other research suggests that the subgroups Lower Centaurus–Crux (LCC) and Upper Centaurus–Lupus (UCL), of the Scorpius–Centaurus association created both the Local Bubble and the Loop I Bubble, with LCC being responsible for the Local Bubble and UCL being responsible for the Loop I Bubble. It was found that 14 to 20 supernovae originated from LCC and UCL, which could have formed these bubbles.