Cat's Eye Nebula
ly[note 1] ly | |
---|---|
Absolute magnitude (V) | −0.2+0.8 −0.6B[note 2] |
Notable features | complex structure |
Designations | NGC 6543,[1] Snail Nebula,[1] Sunflower Nebula,[1] (includes IC 4677),[1] Caldwell 6 |
The Cat's Eye Nebula (also known as NGC 6543 and Caldwell 6) is a planetary nebula in the northern constellation of Draco, discovered by William Herschel on February 15, 1786. It was the first planetary nebula whose spectrum was investigated by the English amateur astronomer William Huggins, demonstrating that planetary nebulae were gaseous and not stellar in nature. Structurally, the object has had high-resolution images by the Hubble Space Telescope revealing knots, jets, bubbles and complex arcs, being illuminated by the central hot planetary nebula nucleus (PNN).[3] It is a well-studied object that has been observed from radio to X-ray wavelengths.
General information
NGC 6543 is a high
phase.NGC 6543 is 4.4
Observations show the bright nebulosity has temperatures between 7000 and 9000
Surface temperature for the central PNN is about 80,000 K, being 10,000 times as luminous as the sun. Stellar classification is O7 + [WR]-type star.[6] Calculations suggest the PNN is over one solar mass, from a theoretical initial 5 solar masses.[8] The central Wolf–Rayet star has a radius of 0.65 R☉ (452,000 km).[9] The Cat's Eye Nebula, given in some sources, lies about three thousand light-years from Earth.[10]
Observations
The Cat's Eye was the first planetary nebula to be observed with a
Infrared observations
Observations of NGC 6543 at
Infrared emission also reveals the presence of
Optical and ultraviolet observations
The Hubble Space Telescope image produced here is in false colour, designed to highlight regions of high and low
X-ray observations
In 2001, observations at
Distance
Planetary nebulae distances like NGC 6543 are generally very inaccurate and not well known.[21] Some recent Hubble Space Telescope observations of NGC 6543 taken several years apart determine its distance from the angular expansion rate of 3.457 milliarcseconds per year. Assuming a line of sight expansion velocity of 16.4 km·s−1, this implies that NGC 6543's distance is 1001±269 parsecs (3×1019 k or 3300 light-years) away from Earth.[22] Several other distance references, like what is quoted in SIMBAD in 2014 based on Stanghellini, L., et al. (2008) suggest the distance is 1623 parsecs (5300 light-years).[23]
Age
The angular expansion of the nebula can also be used to estimate its age. If it has been expanding at a constant rate of 10 milliarcseconds a year, then it would take 1000±260 years to reach a diameter of 20 arcseconds. This may be an upper limit to the age, because ejected material will be slowed when it encounters material ejected from the star at earlier stages of its evolution, and the interstellar medium.[22]
Composition
Like most astronomical objects, NGC 6543 consists mostly of hydrogen and helium, with heavier elements present in small quantities. The exact composition may be determined by spectroscopic studies. Abundances are generally expressed relative to hydrogen, the most abundant element.[7]
Different studies generally find varying values for elemental abundances. This is often because
However, results for NGC 6543 broadly agree that, relative to hydrogen, the helium abundance is about 0.12, carbon and nitrogen abundances are both about 3×10−4, and the oxygen abundance is about 7×10−4.[13] These are fairly typical abundances for planetary nebulae, with the carbon, nitrogen and oxygen abundances all larger than the values found for the sun, due to the effects of nucleosynthesis enriching the star's atmosphere in heavy elements before it is ejected as a planetary nebula.[24]
Deep spectroscopic analysis of NGC 6543 may indicate that the nebula contains a small amount of material which is highly enriched in heavy elements; this is discussed below.[13]
Kinematics and morphology
The Cat's Eye Nebula is structurally a very complex nebula, and the mechanism or mechanisms that have given rise to its complicated morphology are not well understood.[14] The central bright part of the nebula consists of the inner elongated bubble (inner ellipse) filled with hot gas. It, in turn, is nested into a pair of larger spherical bubbles conjoined together along their waist. The waist is observed as the second larger ellipse lying perpendicular to the bubble with hot gas.[25]
The structure of the bright portion of the nebula is primarily caused by the interaction of a fast stellar wind being emitted by the central PNN with the visible material ejected during the formation of the nebula. This interaction causes the emission of X-rays discussed above. The stellar wind, blowing with the velocity as high as 1900 km/s, has 'hollowed out' the inner bubble of the nebula, and appears to have burst the bubble at both ends.[14]
It is also suspected that the central WR:+O7 spectral class PNN star, HD 164963 / BD +66 1066 / PPM 20679
Outside the bright inner portion of the nebula, there are a series of concentric rings, thought to have been ejected before the formation of the planetary nebula, while the star was on the asymptotic giant branch of the Hertzsprung–Russell diagram. These rings are very evenly spaced, suggesting that the mechanism responsible for their formation ejected them at very regular intervals and at very similar speeds.[5] The total mass of the rings is about 0.1 solar masses.[28] The pulsations that formed the rings probably started 15,000 years ago and ceased about 1000 years ago, when the formation of the bright central part began (see above).[29]
Further, a large faint halo extends to large distances from the star. The halo again predates the formation of the main nebula. The mass of the halo is estimated as 0.26–0.92 solar masses.[28]
See also
- List of largest nebulae
Notes
References
- ^ a b c d e f g h i (SIMBAD 2006)
- ^ a b (Reed et al. 1999)
- Bibcode:1985PhDT........13S.
- ^ (Reed et al. 1999, p. 2433)
- ^ a b (Balick, Wilson & Hajian 2001, p. 354)
- ^ a b c (Wesson & Liu 2004, pp. 1026, 1028)
- ^ a b (Wesson & Liu 2004, p. 1029)
- ^ (Bianchi, Cerrato & Grewing 1986)
- ^ Constellation Guide
- ^ Nemiroff, R.; Bonnell, J., eds. (13 May 2007). "The Cat's Eye Nebula From Hubble". Astronomy Picture of the Day. NASA. Retrieved October 26, 2011.
- . See p. 438, "No. 4373".
- ^ (Kwok 2000, p. 1)
- ^ a b c (Wesson & Liu 2004, pp. 1026–1027, 1040–1041)
- ^ a b c d (Balick & Preston 1987, pp. 958, 961–963)
- ^ (Klaas et al. 2006, p. 523)
- ^ (Hora et al. 2004, p. 299)
- ^ (Wesson & Liu 2004, pp. 1027–1031)
- ^ (Chu et al. 2001)
- ^ (Guerrero et al. 2001)
- ^ (Kastner et al. 2012)
- ^ (Reed et al. 1999, p. 2430)
- ^ a b (Reed et al. 1999, pp. 2433–2438)
- S2CID 119257242.
- ^ (Hyung et al. 2000)
- ^ (Reed et al. 1999, pp. 2438–2440)
- ^ (Balick & Preston 1987)
- ^ (Miranda & Solf 1992)
- ^ a b (Balick, Wilson & Hajian 2001, p. 358)
- ^ (Balick, Wilson & Hajian 2001, pp. 359–360)
Cited sources
- Balick, Bruce; Preston, Heather L. (October 1987), "A wind-blown bubble model for NGC 6543", Astronomical Journal, 94: 958–963, doi:10.1086/114528
- Balick, Bruce; Wilson, Jeanine; Hajian, Arsen R. (2001), "NGC 6543: The Rings Around the Cat's Eye", Astronomical Journal, 121 (1): 354–361, doi:10.1086/318052
- Bianchi, L.; Cerrato, S.; Grewing, M. (November 1986), "Mass loss from central stars of planetary nebulae—the nucleus of NGC 6543", Astronomy and Astrophysics, 169 (1–2): 227–236, Bibcode:1986A&A...169..227B
- Chu, You-Hua; Guerrero, Martı´n A.; Gruendl, Robert A.; Williams, Rosa M.; et al. (2001), "Chandra reveals the X-ray glint in the cat's eye", Astrophysical Journal, 553 (1): L69–L72, S2CID 18254815
- Guerrero, Martín A.; Chu, You-Hua; Gruendl, Robert A.; Williams, Rosa M.; et al. (2001), "The Enigmatic X-Ray Point Sources at the Central Stars of NGC 6543 and NGC 7293", Astrophysical Journal, 553 (1): L55–L58, S2CID 18199443
- Hora, Joseph L.; Latter, William B.; doi:10.1086/422820
- Hyung, S.; Aller, L. H.; Feibelman, W. A.; Lee, W. B.; et al. (2000), "The optical spectrum of the planetary nebula NGC 6543",
- Kastner, J.; Montez, R. Jr.; Balick, B.; Frew, D. J.; et al. (2012), "The Chandra X-Ray Survey of Planetary Nebulae (CHANPLANS): Probing Binarity, Magnetic Fields, and Wind Collisions", Astronomical Journal, 144 (2): 18, )
- Klaas, U.; Walker, S. J.; Müller, T. G.; Richards, P. J.; et al. (2006), "Multi-aperture photometry of extended IR sources with ISOPHOT. I. The nature of extended IR emission of planetary Nebulae", Astronomy and Astrophysics, 452 (2): 523–535,
- ISBN 978-0-521-62313-1
- Miranda, L. F.; Solf, J. (1992), "Long-slit spectroscopy of the planetary nebula NGC 6543—Collimated bipolar ejections from a precessing central source?", Astronomy and Astrophysics, 260 (1–2): 397–410, Bibcode:1992A&A...260..397M
- Moore, S. L. (2007), "Observing the Cat's Eye Nebula", Journal of the British Astronomical Association, 117 (5): 279–280, Bibcode:2007JBAA..117R.279M
- Reed, Darren S.; Balick, Bruce; Hajian, Arsen R.; Klayton, Tracy L.; et al. (1999), "Hubble Space Telescope Measurements of the Expansion of NGC 6543: Parallax Distance and Nebular Evolution", Astronomical Journal, 118 (5): 2430–2441, S2CID 14746840
- SIMBAD (December 22, 2006), Results for Cat's Eye Nebula
- Wesson, R.; Liu, X.-W. (2004), "Physical conditions in the planetary nebula NGC 6543", Monthly Notices of the Royal Astronomical Society, 351 (3): 1026–1042,
External links
- Cat's Eye Nebula Release at ESA/Hubble
- Cat's Eye Nebula images at ESA/Hubble
- Chandra X-Ray Observatory Photo Album: NGC 6543
- Astronomy Picture of the Day
- The Cat's Eye Nebula October 31, 1999
- Halo of the Cat's Eye 2010 May 9
- The Cat's Eye Nebula 2016 July 3
- Hubble Probes the Complex History of a Dying Star—HubbleSite article about the Cat's Eye Nebula.
- NGC6543 The Cats Eye Nebula
- Hubble's Color Toolbox: Cat's Eye Nebula—article showing image composite process used to produce an image of the nebula
- Cat's Eye Nebula on
- Cat's Eye Nebula at Constellation Guide
- Cat's Eye Nebula in the Staracle NGC catalog
- SEDS – NGC 6543