Veil Nebula
From Wikipedia, the free encyclopedia
| Diffuse nebula | Lists of nebulae |
|---|---|
 (Eastern half: NGC 6992/95) |
|
| Observation data (Epoch J2000.0) |
|
| Type | Supernova Remnant |
| Right ascension | 20h 46m 08.0s |
| Declination | +30° 42m 30.0s |
| Distance | ?? ly |
| Apparent magnitude (V) | 7.0 |
| Apparent dimensions (V) | 3 degrees |
| Constellation | Cygnus |
| Physical characteristics | |
| Radius | ?? |
| Absolute magnitude (V) | ??? |
| Notable features | |
| Other designations | |
| edit | |
The Veil Nebula, also known as the Cygnus Loop, is a large, relatively faint supernova remnant in the constellation Cygnus. The source supernova exploded some 5000 to 8000 years ago, and the remnants have since expanded to cover an area of 3 degrees. The distance to the nebula is not precisely known, with estimates ranging from 1400 to 2600 light years. It 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."
The Hubble Space Telescope captured images of the nebula. The analysis of the emissions from the nebula indicate the presence of oxygen, sulfur, and hydrogen.
When finely resolved, some parts of the image appear to be ropelike filaments. The standard explanation is that the shock waves are so thin, less than one part in 50,000 of the radius[1], that the shell is only visible 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.
The nebula is notorious among astronomers for being difficult to see visually, even though it has a bright integrated magnitude of 7. However, a telescope using an OIII filter (a filter isolating the wavelength of light from doubly ionized oxygen), will allow an observer to see the nebula clearly, as almost all light from this nebula is emitted at this wavelength. Using an 8-inch telescope equipped with an OIII filter, one could easily see the delicate lacework apparent in photographs. With an OIII filter, almost any telescope could conceivably see this nebula, and some argue that it can be seen without any optical aid, excepting an OIII filter held up to the eye.
The brighter segments of the nebula are listed in the New General Catalog under the designations NGC 6960, 6962, 6979, 6992, and 6995. The easiest segment to find is 6960, which runs through the naked eye star 52 Cygni. A piece of the nebulosity not listed in the NGC is Pickering's Wedge, or Pickering's Triangular Wisp. This segment of nebulosity was discovered photographically by Williamina Fleming, but credit went to her supervisor Edward Pickering and named after Pickering as a result.
[edit] External links
- David Malin/AAO photograph and information
- Amateur astronomer's image
- Other images zoomed out and zoomed farther out.
- An explanation of the image by NASA.
- An explanation of the image by Bill Blair, the astronomer who took it.
