A thin blade of dust and starlight suspended in the dark
NGC 3717 is a striking edge-on spiral galaxy in the constellation Hydra, seen almost perfectly from the side so that its entire disk is compressed into a narrow luminous line. It is classified as SAb? edge-on, indicating an early-type spiral structure whose internal form is revealed dramatically by our viewing angle. The galaxy lies about 59 million light-years away and appears roughly 6.8 × 1.2 arcminutes across, corresponding to a true diameter of about 118,000 light-years
Its most defining feature is the prominent dust lane slicing through the bright central disk, a dense band of interstellar material silhouetted against the combined light of billions of stars. Along the thinner outer disk, faint bluish patches and brighter knots mark regions of ongoing star formation, while the galaxy’s slightly tilted orientation allows its vertical structure and layered stellar disk to stand out with unusual clarity. Most intriguing of all are the extremely faint outer extensions at the ends of the disk, giving NGC 3717 a delicate warped and mildly tidal-like appearance that is often lost in shallower images.
That combination of a razor-thin profile, deep dust structure, and barely visible disturbed outer envelope makes NGC 3717 especially compelling. Around it, the field is filled with countless distant background galaxies, placing this elegant spiral within a much larger cosmic landscape and reminding us how much structure can remain hidden at the threshold of visibility
Imaged in LRGB on the ASA Astrosysteme AZ 1500 at Observatorio El Sauce, Chile.
Image Acquisition and Processing: Mike Selby