Messier 23

Messier 23 (M23) is a 300-million-year-old open star cluster—a grouping of stars that likely formed in the same place but are not gravitationally bound. It’s roughly 2,150 light years from Earth, contains approximately 130 stars, and is about 15 light years in breadth.

N23 is situated in a densely packed region in the Sagittarius constellation not far from the galactic center. Aside from the presence of countless stars in the area, the space between them is filled with ionized gas pockets (red), a number of dark nebulas containing relatively dense, cold gas and dust, and at least three tiny planetary nebulas (labeled “PK” above in the overlay).

Normally, an image of a star cluster of this nature is a boring affair. But sometimes, you find things in images you don’t expect. In this case, there were a couple of surprises—two rarely photographed reflection nebulas that have not been particularly well studied.

Reflection Nebula GM 17.57.8

The first, very near the top of the image just to the right of center, has been catalogued as GN 17.57.8. The only authoritative reference I can find to it is a listing T. Yu. Magakian’s Merged Catalogue of Reflection Nebulae published in 2002. I enlarged and cropped it below so you can get a better look at it:

Southern Nebulous Object 85 (SNO 85)

The second was catalogued as SNO 85 in Nebulous Objects in the Southern Hemisphere in 2004 by A. L. Gyulbudaghian, et al. They described it as “[a] condensation with a cone-like nebula (20 arcsec) at the edge of dark and bright nebulae.” A couple of years later, Gyulbudaghian and May followed up on SNO 85 and determined that it is associated with young stellar objects that may be forming in the dark regions of LDN 288. Again, I’ve enlarged and cropped it here for a better view: