Helix Nebula

Helix Nebula, NGC 7293
Emission nebula
Planetary nebula
	NGC 7293 seen through several visible filters by Hubble Space Telescope
Observation data: J2000 epoch
Right ascension	22h 29m 38.55s
Declination	−20° 50′ 13.6″
Distance	200±1 pc (650±3) ly
Apparent magnitude (V)	+7.6
Apparent dimensions (V)	25′
Constellation	Aquarius
Physical characteristics
Radius	2.87 ly (0.88 pc) ly
Notable features	One of the nearest PNe
Designations	NGC 7293 Caldwell 63
	See also: Lists of nebulae

The Helix Nebula (also known as NGC 7293 or Caldwell 63) is a planetary nebula (PN) located in the constellation Aquarius. Discovered by Karl Ludwig Harding, most likely before 1824, this object is one of the closest of all the bright planetary nebulae to Earth.^[3] The distance, measured by the Gaia mission, is 655±13 light-years.^[4] It is similar in appearance to the Cat's Eye Nebula and the Ring Nebula, whose size, age, and physical characteristics are similar to the Dumbbell Nebula, varying only in its relative proximity and the appearance from the equatorial viewing angle.^[5] The Helix Nebula has sometimes been referred to as the "Eye of God" in pop culture,^[6] as well as the "Eye of Sauron".^[7]^[8]

^ ^a ^b ^c ^d "NGC 7293". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-12-07.
^ ^a ^b Cite error: The named reference ODelletal2004 was invoked but never defined (see the help page).
^ Hora, Joseph L.; Latter, William B.; Smith, Howard A.; Marengo, Massimo (2006). "Infrared Observations of the Helix Planetary Nebula". The Astrophysical Journal. 652 (1): 426–441. arXiv:astro-ph/0607541. Bibcode:2006ApJ...652..426H. doi:10.1086/507944. S2CID 15427995.
^ "SIMBAD references".
^ O'Dell, C. R.; Balick, B.; Hajian, A. R.; Henney, W. J.; et al. (2002). "Knots in Nearby Planetary Nebulae". The Astronomical Journal. 123 (6): 3329–3347. Bibcode:2002AJ....123.3329O. doi:10.1086/340726.
^ "Urban Legends Reference Pages". The Eye of God. 5 February 2004. Retrieved 2007-07-16.
^ "The Eye of Sauron (aka NGC7293)". Sky and Telescope.
^ Nancy Atkinson (4 October 2012). "Eye-Like Helix Nebula Turns Blue in New Image". Universe Today. Archived from the original on 14 July 2014.

[simbad-1] "NGC 7293". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-12-07.

[ODelletal2004-2] Cite error: The named reference ODelletal2004 was invoked but never defined (see the help page).

[Horaetal2006-3] Hora, Joseph L.; Latter, William B.; Smith, Howard A.; Marengo, Massimo (2006). "Infrared Observations of the Helix Planetary Nebula". The Astrophysical Journal. 652 (1): 426–441. arXiv:astro-ph/0607541. Bibcode:2006ApJ...652..426H. doi:10.1086/507944. S2CID 15427995.

[4] "SIMBAD references".

[ODelletal2002-5] O'Dell, C. R.; Balick, B.; Hajian, A. R.; Henney, W. J.; et al. (2002). "Knots in Nearby Planetary Nebulae". The Astronomical Journal. 123 (6): 3329–3347. Bibcode:2002AJ....123.3329O. doi:10.1086/340726.

[6] "Urban Legends Reference Pages". The Eye of God. 5 February 2004. Retrieved 2007-07-16.

[7] "The Eye of Sauron (aka NGC7293)". Sky and Telescope.

[8] Nancy Atkinson (4 October 2012). "Eye-Like Helix Nebula Turns Blue in New Image". Universe Today. Archived from the original on 14 July 2014.

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