NGC 6210 — Planetary Nebula in Hercules

NGC 6210 is a small, bright planetary nebula in Hercules, about 5,000 light-years away. Its central disc is round and intensely bright at magnitude 8.8, but Hubble Space Telescope imaging revealed a startlingly complex envelope around it: a series of bipolar lobes, jets, and curved bubbles that together resemble a cosmic turtle, giving the object its informal nickname. The small angular size — only about 20 arcseconds across in the bright core — concentrates its light into one of the highest surface brightnesses of any northern planetary, making it almost stellar in appearance at low magnification.

A 4-inch at low power shows NGC 6210 essentially as a slightly fuzzy bluish star — easy to overlook unless you know what to look for. Push the magnification to 200-300x and the small disc resolves into a distinct round patch with a clear blue-green tint. An 8-inch at 400x begins to suggest asymmetry in the disc and the very faint outer extensions, but the elaborate turtle structure visible in HST images is purely photographic. Star-hop from Beta Herculis (Kornephoros) about 4 degrees northeast. Best observed April through August.

Discovered by Friedrich Georg Wilhelm von Struve in 1825 during his observations at the Dorpat Observatory. The complex structure of the outer envelope was first revealed in the 1990s by HST imaging, which transformed NGC 6210 from a nondescript bright dot into one of the most morphologically interesting planetaries known.