Pickering's Triangle is a small
part of the Veil Nebula. The Veil Nebula is a cloud of heated and ionized gas
and dust in the constellation Cygnus.
The source supernova was a star
20 times more massive than the Sun, which exploded around 8,000 years ago. The
remnants have since expanded to cover an area of the sky roughly 3 degrees in
diameter (about 6 times the diameter of the full Moon). The distance to the
nebula is not precisely known, but data suggests a distance of about 1,470
light-years.
The analysis of the emissions
from the nebula indicate the presence of Sulphur (Sii), Hydrogen (Ha) and
Oxygen (Oiii). In this image, these wavelengths have been mapped to the Red,
Green and Blue channels respectively; this is commonly known as the Hubble
Palette (SHO). Almost all of the light from this nebula is emitted in the
Oxygen wavelength, giving a predominantly blue colour. The deep orange
areas are a mixture of Sulphur and Hydrogen.
Some parts of the image appear to
be rope-like filaments. The standard explanation is that the shock waves are so
thin that the shell is visible only when viewed exactly edge-on, giving the
shell the appearance of a filament.
Even though the nebula has a
relatively bright integrated magnitude of 7, it is spread over so large an area
that the surface brightness is quite low, so the nebula is notorious among
astronomers for being difficult to see. However, apparently it can be seen
clearly in a telescope using an Oiii filter (a filter isolating the wavelength
of light from doubly ionized oxygen).
This image is 16x180secs each Sii, Ha and Oiii, filters with
Darks, Flats and Bias. Processed in PixInsight and finished in Photoshop.
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