Close Stars To The Solar System
The Orion–Eridanus Superbubble, or Eridanus Soft X-ray Enhancement is a superbubble located west of the Orion Nebula. The region is formed from overlapping supernova remnants that may be associated with the Orion OB1 stellar association; the bubble is approximately 1200 ly across. It is the nearest superbubble to the Local Bubble containing the Sun, with the respective shock fronts being about 500 ly apart.
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 and the G-cloud. (The Local Interstellar Cloud contains our 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 that 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. 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.