Veil Nebula
| Diffuse nebula | |
|---|---|
| supernova remnant | |
Western Veil nebula
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| Observation data: J2000.0 epoch | |
| Right ascension | 20h 45m 38.0s |
| Declination | +30° 42′ 30″ |
| Distance | 1470 ly |
| Apparent magnitude (V) | 7.0 |
| Apparent dimensions (V) | 3 degrees (diameter) |
| Constellation | Cygnus |
| Physical characteristics | |
| Radius | 50 ly |
| Designations | NGC 6960, 6992, 6995, 6974, and 6979, IC 1340, Cygnus Loop, Cirrus Nebula, Filamentary Nebula, Witch's Broom Nebula (NGC 6960),Caldwell 33/34 |
The Veil Nebula is a cloud of heated and ionized gas and dust in the constellation Cygnus. It constitutes the visible portions of the Cygnus Loop (radio source W78, or Sharpless 103), a large but relatively faint supernova remnant. The source supernova exploded circa 3,000 BC to 6,000 BC, and the remnants have since expanded to cover an area roughly 3 degrees in diameter (about 6 times the diameter, or 36 times the area, of the full moon). The distance to the nebula is not precisely known, but Far Ultraviolet Spectroscopic Explorer (FUSE) data supports a distance of about 1,470 light-years.
The Hubble Space Telescope captured several images of the nebula. The analysis of the emissions from the nebula indicate the presence of oxygen, sulfur, and hydrogen. This is also one of the largest, brightest features in the x-ray sky.
September 24, 2015 new images and videos of the Veil Nebula were released, with an explanation of the images.
In modern usage, the names Veil Nebula, Cirrus Nebula, and Filamentary Nebula generally refer to all the visible structure of the remnant, or even to the entire loop itself. The structure is so large that several NGC numbers were assigned to various arcs of the nebula. There are three main visual components:
NGC 6974 and NGC 6979 are luminous knots in a fainter patch of nebulosity on the northern rim between NGC 6992 and Pickering's Triangle.
The nebula was discovered on 1784 September 5 by William Herschel. He described the western end of the nebula as "Extended; passes thro' 52 Cygni... near 2 degree in length", and described the eastern end as "Branching nebulosity... The following part divides into several streams uniting again towards the south."
When finely resolved, some parts of the image appear to be rope-like filaments. The standard explanation is that the shock waves are so thin, less than one part in 50,000 of the radius, that the shell is visible only when viewed exactly edge-on, giving the shell the appearance of a filament. Undulations in the surface of the shell lead to multiple filamentary images, which appear to be intertwined.
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