Orion-Eridanus Superbubble in Hα (without continuum; mapped to green), visual continuum (star-reduced and without Hα; mapped to red) and X-rays ((0.2-2.3 keV; mapped to blue). Optical data are from the Northern Sky Narrowband Survey, and X-ray data are from theeROSITA-DE DR1 of the western Galactic hemisphere. X-ray emissions (blue) are visible only through the voids of the molecular clouds (red). HII regions appear green.
TheOrion–Eridanus Superbubble is asuperbubble located in the constellationsOrion andEridanus. The region is formed from overlappingsupernova remnants that were suspected to be associated with theOrion OB1 stellar association. The bubble is approximately 1200 ly across.[1][2] It is the nearest superbubble to theLocal Bubble containing the Sun, with the respective shock fronts being about 500 ly apart.[1][2]
The Orion–Eridanus Superbubble is formed by thestellar wind of tens of massive stars and 10–20supernovae.[3] The superbubble likely formed from theOrion blue stream, which is composed of massive stars in front of theOrion Molecular Cloud Complex. The Orion blue stream begins at around 150parsec and extends towards Orion OB1 at around 300 parsec. The stream could however include theBellatrix cluster, which is around 80 parsec distant.[4]
The structure was discovered from21 cm radio observations byCarl Heiles and interstellar optical emission line observations by Reynolds and Ogden in the 1970s.[5] The western part of the Orion–Eridanus Superbubble is visible in X-ray images and is therefore also referred to as theEridanus Soft X-ray Enhancement. In the eastern part, these wavelengths are obscured by molecular clouds, making it impossible to determine the morphology from X-rays alone (see also the anti-correlation between the reddish molecular clouds and the blue X-ray emission in the image above).
Older works considerBarnard's Loop to be either the nearest[6] or the most distant[7] edge of the Orion–Eridanus Superbubble, assuming that theλ Orionis Nebula lies outside. More recent studies suggest that the superbubble extends to the Galactic plane and that both Barnard's Loop and the λ Orionis Nebula lie inside.[8] The exact morphology and orientation in space remain uncertain.
TheSun might have passed through the Orion–Eridanus Superbubble before it passed through the Local Bubble. This could explain an older peak ofiron-60 found indeep sea sediments.[9]
^abAschenbach, B.; Hermann-Michael Hahn; Joachim Truemper (1998).The invisible sky: ROSAT and the age of X-ray astronomy. Springer.ISBN978-0-387-94928-4.
