This is the portion of the Veil Nebula known as Pickering's Triangular Wisp, Pickering's Triangle, or Fleming's Triangle.

The triangle was actually discovered by Williamina Fleming in 1904 on photographic plates at Harvard Observatory, but it was named after Edward Charles Pickering, the observatory's director, as was the common practice at that time.

The triangle was discovered after the New General Catalogue (NGC) was published, so it does not have an NGC number. It does have a catalog designation of Simeis 3-188.

The Veil Nebula is the supernova remnant from a star that exploded 5,000 to 10,000 years ago. It is located 1,400 to 2,500 light-years away in the constellation of Cygnus.

North is to the left in the above image.

Simeis 3-188 Catalogs: Simeis 3-188 Common Name: Pickering's Triangular Wisp Pickering's Triangle Fleming's Triangle Object Type: Supernova Remnant Size: 120' x 60' Constellation: Cygnus Image Field Centered At: RA: 20h 48m 27s Dec: +31° 31' 55"