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| Lambda Orionis ring | |
|---|---|
| Name | Lambda Orionis ring |
| Type | Ring-shaped molecular and H II region |
| Epoch | J2000 |
| Constellation | Orion |
| Distance | ~1,100 ly |
| Radius | ~50 pc |
| Major star | Lambda Orionis |
Lambda Orionis ring The Lambda Orionis ring is a prominent ring-shaped nebular structure in the Orion complex surrounding the star Meissa (Lambda Orionis). It forms part of a larger network of molecular clouds and emission nebulosity that includes well-known regions such as the Orion Molecular Cloud Complex, Barnard's Loop, and the Horsehead Nebula. The ring is associated with an H II region and multiple young stellar objects, and it has been the subject of multiwavelength studies by observatories like IRAS, Spitzer Space Telescope, and Herschel Space Observatory.
The structure encircles the OB association centered on Meissa and links to nearby clouds including Lynds 1630, Lynds 1641, and parts of the Orion B molecular cloud. It is visible in radio, infrared, and optical emission, often mapped alongside features such as Barnard 30, Barnard 35, and the stellar aggregate around Collinder 69. The ring's extent and morphology have been characterized using surveys from facilities like NRAO radio telescopes, the European Southern Observatory, and the Submillimeter Array.
The ring exhibits a cavity of ionized hydrogen bounded by a shell of molecular gas and dust traced in CO, HI, and far-infrared continuum. Observations measure column densities and velocity dispersions across clumps in catalogued clouds such as L1630N and L1622. Typical properties include electron temperatures similar to other Galactic H II regions studied by William Herschel Telescope teams, and dust temperatures comparable to sources in surveys by the Planck mission. The ring's kinematics show expansion signatures compatible with superbubble dynamics analyzed in studies referencing the Local Bubble and shells like the Loop I structure.
Proposed formation scenarios invoke feedback from massive stars, including stellar winds, photoionization, and one or more supernovae from early generations within the Orion OB1 association. Models utilize hydrodynamic simulations developed by groups at institutions such as the Max Planck Institute for Astronomy, Harvard-Smithsonian Center for Astrophysics, and Princeton University to reproduce shell formation observed in surveys by ALMA and the Very Large Array. Alternative hypotheses consider cloud–cloud collision mechanisms similar to those proposed for structures like the Perseus molecular cloud and the Taurus Molecular Cloud. Constraints come from age dating of clusters such as Collinder 69 and comparison with stellar evolution tracks from the Geneva Observatory and Padova models.
The ring contains young clusters, protostars, and pre-main-sequence stars cataloged in surveys by the Two Micron All Sky Survey and the Sloan Digital Sky Survey. Notable associated objects include the open cluster Collinder 69, infrared sources catalogued by IRAS and WISE, and Herbig–Haro objects studied by teams from California Institute of Technology and University of Hawaii. Stellar population analyses reference spectral classifications from the Henry Draper Catalogue and kinematic membership work using data from the Gaia mission, linking the ring's population to subgroups within the Orion OB1 association.
The feature was first noted in photographic and visual catalogs compiled by astronomers at observatories such as Mount Wilson Observatory and the Royal Greenwich Observatory. Radio mapping and CO surveys by researchers at the Harvard College Observatory and Nobeyama Radio Observatory clarified its molecular content. Infrared imaging by the Infrared Astronomical Satellite and later by Spitzer Space Telescope and Herschel Space Observatory revealed dust shells and embedded protostars. Recent analyses have employed data from Gaia for astrometry, Chandra X-ray Observatory for high-energy emission, and ground-based spectrographs at Keck Observatory and the European Southern Observatory to refine ages and dynamics.
The Lambda Orionis ring is spatially and dynamically linked to the larger Orion Molecular Cloud Complex and delineates a complementary structure to Barnard's Loop, which itself is a large emission arc associated with past energetic events in the Orion region. Comparative studies reference the Orion A and Orion B clouds, examine connections to the Eridanus superbubble, and situate the ring within Galactic plane surveys such as those by COBE and Planck. Researchers from institutions like Columbia University and the Max Planck Institute for Astrophysics use the ring as a case study for feedback-driven shell evolution and triggered star formation observed across the Milky Way.
Category:Orion (constellation) Category:H II regions Category:Molecular clouds