 the local bubble is a cavity in the interstellar medium (ism) in the orion arm of the milky way. it contains, among others, the local interstellar cloud, g-cloud, and the solar system. it is at least 300 light years across and has a 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 of the local interstellar cloud (0.3 atoms/cm3). the hot diffuse gas in the local bubble emits x-rays. the very sparse, hot gas of the local bubble is the result of supernovae that exploded within the past ten to twenty million years.local chimney and superbubbles, solstation.comnasa-funded x-ray instrument settles interstellar debate, www.nasa.gov it was once thought that the most likely candidate for the remains of this supernova was geminga ("gemini gamma-ray source"), a pulsar in the constellation gemini. more recently, however, it has been suggested that multiple supernovae in subgroup b1 of the pleiades moving group were more likely responsible, becoming a remnant supershell.{{cite web |url= http://aas.org/archives/baas/v29n5/aas191/abs/s051009.html |title= [51.09] model of an expanding supershell structure i
Interstellar_media Objects_within_1000_ly_of_Earth