Veil nebula

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Veil nebula
Veil Nebula - NGC6960.jpg
Observational Data
Designation Various
Right ascension 20h 45m 38.0s[1]
Declination +30° 42′ 30″[1]
Constellation Cygnus
Type of object Supernova remnant
Dimensions 3° across[1]
Magnitude Apparent Mag: +7.0[1]
Absolute Mag: -1.3[2]
Astrometry
Distance from Earth 1,470 ly[1]

The Veil nebula is a large nebula in the constellation of Cygnus.[3] The name of the nebula derives from the draped, filamentary structures within the nebula. The nebula is part of the Cygnus loop and its closeness compared to other nebulae make it an excellent target for amateur astronomers. The nebula has several names including: Witch’s broom nebula, Bridal Veil nebula, Cirrus nebula, or Filamentary nebula.

History of observation

Parts Veil nebula was first observed on September 5, 1784 by William Herschel.[1] Some regions in the Eastern Veil nebula were missed by William Herschel and were subsequently discovered by John Herschel.[4] Ebenezer Porter Mason made detailed observations of the Eastern region which have today been shown to be accurate. Later in 1904, Williamnina Flemning at Harvard Observatory discovered a fainter region of the nebula not observed by Herschel known as Flemning's Triangle. Although discovered by Flemning, it was originally named Pickering's Triangle after the Edward Charles Pickering, the director of the Harvard Observatory at the time.

Properties and structure

The nebula is situated 2,100 light years away from Earth, though some sources suggest it is closer at 1,470 ly.[5][6] The nebula is around 110 ly across, corresponding to an apparent size of 3 degrees.[7] It covers an area of the night sky equal to around six full Moons. The debris in the nebula is moving rapidly at roughly 600,000 kilometres per hour.[1] This results in shock fronts forming that heat the gas in the nebula to millions of kelvin. The material then glows as it cools. Although bright, the large area results in a low surface brightness and an OIII filter is recommended for observations.[8] The brightness of the nebula varies across the nebula due to variations in the density of the gas present in the nebula, with denser regions being brighter.[9]

Observations of the nebula in non-optical regions of the electromagnetic spectrum have revealed many interesting facts about the nebula. The nebula is a source of radio emissions and possess the designations W87 and Shapeless 101 for this.[10] It is also one of the largest and brightest sources of x-rays in the night sky.[11][12] The x-ray spectrum of the nebula has indicated it contains the elements sulfur, oxygen and hydrogen. The supernova remnant at the centre of the nebula is an x-ray source with designation Cygnus X-5.[1] When viewed in ultraviolet, gas that has been heated to extreme temperatures by shockwaves is easily identifiable.[13]

The nebula is large and is commonly considered to be composed of three regions, the Eastern Veil nebula, the West Veil nebula and Fleming’s Triangle (sometimes called Pickering’s Triangle).[1] The regions and features of the nebula have numerous designations in the New General Catalogue including NGC 6960, NGC 6992, NGC 6995, NGC 6974, and NGC 6979. Additionally the southern region of the Eastern Veil nebula has the designation IC 1340.

Eastern Veil nebula

Designated NGC 6992 and Caldwell 33, the Eastern Veil nebula is comprised of several interwoven strands of glowing gas.[9] The luminous arc of gas and dust at the south of the Eastern Veil nebula is designated NGC 6995 and together with NGC 6992 is sometimes referred to as the Network nebula. The arc is over one degree long.[9]

Western Veil nebula

The Western Veil nebula (NGC 6960) is also known as the Witch's Broom. This region of the Veil nebula is very easy to locate as it lies behind the star 52 Cygni which can be observed without binoculars. The region spans a distance of 35 ly.[1] Like the Veil nebula as a whole, this region has many names including: Filamentary Nebula, Finger of God Nebula, Lace-work Nebula as well as Caldwell 34.

Flemning's Triangle

Also known as Pickering’s Triangle, Flemning's Triangle can be found at in the northern area of the Veil nebula, where it runs from the top to the centre region of the nebula. Unsurprisingly, it has a roughly triangular shape and contains numerous "knots" where the gas is brighter and has a complex structure. The southernmost knot is an extreme source of x-rays. Alternative names for the region include: Pickering’s Triangular Wisp or Pickering’s Wedge.

Gallery

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 Veil nebula. constellation-guide.com. Retrieved on December 23, 2019.
  2. From definition of absolute magnitude, using apparent magnitude (+7.0) and distance (2,100 ly) given here.
  3. Veil Nebula Supernova Remnant. nasa.gov (September 24, 2015). Retrieved on December 23, 2019.
  4. Shears, Jeremy; Knight, Carl; Lewis, Martin et al.. "In the footsteps of Ebenezer Porter Mason and his nebulae". Journal of the British Astronomical Association.  arXiv:1401.7960
  5. The Cygnus Loop. phys.org (November 27, 2018). Retrieved on December 23, 2019.
  6. Fesen, R. A.; Neustadt, J. M. M.; Black, C. S. et al. (2018). "A Distance Estimate to the Cygnus Loop Based on the Distances to Two Stars Located Within the Remnant". Monthly Notices of the Royal Astronomical Society 475 (3): 3996-4010. doi:10.1093/mnras/sty072. Bibcode2018MNRAS.475.3996F.  arXiv:1711.02174
  7. The Ghostly Veil Nebula. apod.nasa.gov (October 31, 2019). Retrieved on December 23, 2019.
  8. NGC 6960, 6979, 6992, 6995: The Veil Nebula. spider.seds.org. Retrieved on December 23, 2019.
  9. 9.0 9.1 9.2 Bob King (September 15, 2018). Explore the Veil Nebula. skyandtelescope.com. Retrieved on December 23, 2019.
  10. Cygnis Loop. britannica.com. Retrieved on December 23, 2019.
  11. McEntaffer, R. L.; Cash, W. (2008). "Soft X-ray Spectroscopy of the Cygnus Loop Supernova Remnant". The Astrophysical Journal 600 (1): 328-335. doi:10.1086/587936. Bibcode2008ApJ...680..328M.  arXiv:0801.4552
  12. Soft X-ray Emission from the Cygnus Loop. heasarc.gsfc.nasa.gov (July 02, 2007). Retrieved on December 23, 2019.
  13. Cygnus Loop Nebula. nasa.gov (March 22, 2012). Retrieved on December 23, 2019.