The Heart of the Swan

M17 is a large emission nebula in Sagittarius, similar to that in Orion, but viewed edge-on instead of face-on. Its rather complex and irregular shape has spawned a variety of descriptive monikers, including: Swan Nebula, Omega Nebula, Checkmark Nebula, and Horseshoe Nebula.

The nebulosity extends out considerably more than this image shows, but we wanted to concentrate on the central portion, which is richer in the OIII emission.

Small scale detail is preserved (and enhanced) in this completely narrowband version of M17, whereas it often appears relatively washed out in other M17 versions that use broadband data. Of course, it helps that our image scale at CTIO is 0.4"/pixel, and the FWHM of 30 minute integrations routinely approaches 1.0" (before any deconvolution or other sharpening)!