Sh2-126, commonly known as the Great Lacerta Nebula, is a large but faint emission nebula located within the constellation Lacerta. The nebula is predominantly composed of hydrogen gas, which emits a distinct red glow due to ionization from strong ultraviolet radiation, mainly from the blue main sequence star 10 Lacertae.
Location and Structure
• Sh2-126 is part of Lacerta OB1, a star-forming region approximately 1,200 light-years from Earth.
• The nebula stretches across about 3 by 2 degrees of the sky, requiring a wide field of view to capture its entirety.
• Embedded within the nebula is LBN 437, a molecular cloud with dense regions associated with young stars, as well as a notable reflection nebula around the Herbig Ae/Be star V375 Lacertae.
Astrophotography Insights
• The emission region presents little overall structure, and while larger telescopes do not necessarily reveal more detail, imaging with a hydrogen-alpha filter can effectively bring out its faint features.
• The nebula is best imaged with a wide-field setup, and significant exposure times are typically necessary for high signal-to-noise ratios due to its faintness.
• OIII filters are not particularly effective for this object, as its emission is dominated by hydrogen-alpha.
Scientific Interest
• Sh2-126 is a site of ongoing star formation, evidenced by its association with young stars and the presence of Herbig-Haro objects—small nebulae formed by jets from young stars impacting nearby dust clouds.
• The nebula is frequently targeted in deep-sky astrophotography for its subtle but extensive hydrogen emission filaments and its position away from the galactic core, offering dark-sky opportunities.
This region is a rich but challenging target for wide-field astrophotographers interested in capturing large emission nebulae and exploring the star-forming environs beyond more prominent nebulae nearer the galactic plane.
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