NGC 7424 — a flocculent spiral revealing the messy art of galaxy building
Like a delicate whirlpool of starlight, NGC 7424 is a face-on spiral galaxy about 37 million light-years away in the constellation Grus. Classified as SAB(rs)cd, it’s an intermediate spiral with loosely wound arms and a small central bar. Measuring roughly 100,000 light-years across — similar in size to the Milky Way — it spans about 5.0 × 4.6 arcminutes on the sky.
This striking spiral displays a flocculent structure: its arms are not smooth and continuous but patchy and fragmented, shaped by bursts of localized star formation rather than a strong density wave. Bright pink H II regions scattered throughout trace sites where massive new stars are forming, while the bluish spiral arms are rich in young stellar populations. Surrounding the main disk, faint and ghostly extensions form a diffuse outer envelope that stretches well beyond the visible spiral, possibly shaped by past minor interactions or slow gas accretion.
NGC 7424 is also notable for its recent stellar deaths. It has hosted multiple core-collapse supernovae — including SN 2001ig and SN 2017bzb — revealing an active population of short-lived, massive stars. At its heart lies a compact nuclear star cluster rather than a large classical bulge, a feature common among late-type spirals.
A quietly spectacular and often overlooked galaxy of the southern skies — a cosmic pinwheel spinning gracefully 37 million years away.
Imaged in LRGB Ha on my Planewave CDK 1000 at Observatorio El Sauce, Chile.
Image acquisition and processing: Mike Selby