The Sadr Region (IC 1318)
A vast emission nebula and H II complex in the constellation Cygnus, draped around the bright central star Sadr (γ Cygni) at the heart of the Northern Cross. Also known as the Gamma Cygni Nebula and the Butterfly Nebula, IC 1318 is one of the most extensive nebulous regions in the summer Milky Way.
The nebula lies roughly 2,000–5,000 light-years from Earth (commonly estimated near 3,500–4,900 ly), well beyond Sadr itself at about 1,800 light-years. Spanning some 3.5° × 2° on the sky, the complex stretches at least 100 light-years across—and may approach 200–300 light-years from side to side depending on its true distance. Brighter lobes within IC 1318 are each on the order of ~50 light-years wide.
Ionized hydrogen glows amid dark dust lanes and mottled gas, forming the winged “butterfly” shapes that make this region a favorite of narrowband and broadband astrophotographers alike.
