NGC 6992, NGC 6995 - The Eastern Veil Nebula

The Veil Nebula is a large, relatively faint supernova remnant in the constellation Cygnus. Also known as the Cygnus Loop or the Witch's Broom Nebula, it is a favorite summer celestial showpiece, especially its eastern segment NGC 6992-95.

The Veil was discovered on 1784 September 5 by William Herschel. It is so large - six times the diameter of the Full Moon - that its brighter parts appeared as a number of distinct diffuse nebulae, and were assigned separate NGC numbers: NGC 6960, 6979, 6992, and 6995. Even William Herschel had them as separate objects: H 2.206 = NGC 6979, H 5.14 = NGC 6992/95, H 5.15 = NGC 6960. He described the eastern end of the nebula as "Branching nebulosity... The following part divides into several streams uniting again towards the south."

Despite its overall brightness of about magnitude 5, this object is only visible to the naked eye under exceptionally good viewing conditions, because its light is distributed over such a large area. NGC 6992 and NGC 6995 are the only parts of the supernova remnant that can be unmistakably seen in binoculars. Look for them 3.5 degrees southeast of Epsilon Cygni and 2.5 degrees northest of 52 Cygni. The Eastern Veil Nebula appears as a faint, hazy, somewhat bloated fishhook, the shaft of which points directly at Epsilon Cygni.

NGC 6992-95 is only a small portion of the eastern side of the Cygnus Loop - a large, almost spherical glowing shell of gas, about three degrees across. The Cygnus Loop is the expanding remains of a star that exploded between 5,000 and 8,000 years ago. The shockwave from the explosion is exciting the tenuous interstellar medium and making it glow. The nebula (and thus its precursor star) is about 1900 light years distant, and about 100 light years across.