7/30/2019 Cat's Eye Nebula
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Cat's Eye Nebula
From Wikipedia, the free encyclopedia
Cat's Eye Nebula
Composite image using optical images from theHSTand
X-ray data from theChandra X-ray Observatory
Observation data
(EpochJ2000)
Right ascension 17h
58m
33.423s[1]
Declination +66 3759.52[1]
Distance 3.3 0.9kly(1.0 0.3kpc)[2]
Apparent
magnitude(V)
9.8B[1]
Apparent
dimensions (V)
Core: 20[2]
Constellation Draco
http://en.wikipedia.org/wiki/Hubble_Space_Telescopehttp://en.wikipedia.org/wiki/Hubble_Space_Telescopehttp://en.wikipedia.org/wiki/Hubble_Space_Telescopehttp://en.wikipedia.org/wiki/Chandra_X-ray_Observatoryhttp://en.wikipedia.org/wiki/Chandra_X-ray_Observatoryhttp://en.wikipedia.org/wiki/Chandra_X-ray_Observatoryhttp://en.wikipedia.org/wiki/Epoch_(astronomy)http://en.wikipedia.org/wiki/Epoch_(astronomy)http://en.wikipedia.org/wiki/J2000http://en.wikipedia.org/wiki/J2000http://en.wikipedia.org/wiki/J2000http://en.wikipedia.org/wiki/Right_ascensionhttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Declinationhttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Light_yearhttp://en.wikipedia.org/wiki/Light_yearhttp://en.wikipedia.org/wiki/Light_yearhttp://en.wikipedia.org/wiki/Parsechttp://en.wikipedia.org/wiki/Parsechttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Reedetal1999-1http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Reedetal1999-1http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Reedetal1999-1http://en.wikipedia.org/wiki/Apparent_magnitudehttp://en.wikipedia.org/wiki/Apparent_magnitudehttp://en.wikipedia.org/wiki/Apparent_magnitudehttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Reedetal1999-1http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Reedetal1999-1http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Reedetal1999-1http://en.wikipedia.org/wiki/Constellationhttp://en.wikipedia.org/wiki/Draco_(constellation)http://en.wikipedia.org/wiki/File:NGC6543.jpghttp://en.wikipedia.org/wiki/Draco_(constellation)http://en.wikipedia.org/wiki/Constellationhttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Reedetal1999-1http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Apparent_magnitudehttp://en.wikipedia.org/wiki/Apparent_magnitudehttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Reedetal1999-1http://en.wikipedia.org/wiki/Parsechttp://en.wikipedia.org/wiki/Light_yearhttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Declinationhttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Right_ascensionhttp://en.wikipedia.org/wiki/J2000http://en.wikipedia.org/wiki/Epoch_(astronomy)http://en.wikipedia.org/wiki/Chandra_X-ray_Observatoryhttp://en.wikipedia.org/wiki/Hubble_Space_Telescope7/30/2019 Cat's Eye Nebula
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Physical characteristics
Radius Core: 0.2ly[note 1]
Absolute
magnitude(V)
0.2+0.8
0.6B[note 2]
Notable features complex structure
Other
designations
NGC6543,[1]
Snail Nebula,[1]
Sunflower Nebula,[1]
(includesIC
4677),[1]
Caldwell 6
See also:Planetary nebula,Lists of nebulae
Coordinates: 17h
58m
33.423s, +66 37 59.52
The Cat's Eye Nebula(NGC6543, Caldwell 6) is aplanetary nebulain the
constellation ofDraco. Structurally, it is one of the most complex nebulae known, with
high-resolutionHubble Space Telescopeobservations revealing remarkable structures
such as knots, jets, bubbles and sinewy arc-like features. In the center of the Cat's Eye
there is a bright and hot star; around 1000 years ago this star lost its outer envelope,producing the nebula.
It was discovered byWilliam Herschelon February 15, 1786, and was the first
planetary nebula whosespectrumwas investigated by the Englishamateur astronomer
William Hugginsin 1864. The results of the latter investigation demonstrated for the
first time that planetary nebulae consist of hot gases, but not stars. Currently the nebula
has been observed across the full electromagnetic spectrum, fromfar-infraredtoX-rays.
Modern studies reveal several mysteries. The intricacy of the structure may be caused in
part by materialejectedfrom abinarycentral star, but as yet, there is no direct evidence
that the central star has a companion. Also, measurements of chemical abundancesreveal a large discrepancy between measurements done by two different methods, the
cause of which is uncertain. Hubble Telescope observations revealed a number of faint
rings around the Eye, which are spherical shells ejected by the central star in the distant
past. The exact mechanism of those ejections, however, is unclear.
Contents
1 General information 2 Observations
o
2.1 Infrared observationso 2.2 Optical and ultraviolet observations
http://en.wikipedia.org/wiki/Radiushttp://en.wikipedia.org/wiki/Light_yearhttp://en.wikipedia.org/wiki/Light_yearhttp://en.wikipedia.org/wiki/Light_yearhttp://en.wikipedia.org/wiki/Light_yearhttp://en.wikipedia.org/wiki/Absolute_magnitudehttp://en.wikipedia.org/wiki/Absolute_magnitudehttp://en.wikipedia.org/wiki/Absolute_magnitudehttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-3http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-3http://en.wikipedia.org/wiki/New_General_Cataloguehttp://en.wikipedia.org/wiki/New_General_Cataloguehttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Index_Cataloguehttp://en.wikipedia.org/wiki/Index_Cataloguehttp://en.wikipedia.org/wiki/Index_Cataloguehttp://en.wikipedia.org/w/index.php?title=IC_4677&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=IC_4677&action=edit&redlink=1http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Planetary_nebulahttp://en.wikipedia.org/wiki/Planetary_nebulahttp://en.wikipedia.org/wiki/Planetary_nebulahttp://en.wikipedia.org/wiki/Category:Lists_of_nebulaehttp://en.wikipedia.org/wiki/Category:Lists_of_nebulaehttp://en.wikipedia.org/wiki/Category:Lists_of_nebulaehttp://en.wikipedia.org/wiki/Celestial_coordinate_systemhttp://en.wikipedia.org/wiki/Celestial_coordinate_systemhttp://www.wikisky.org/?ra=17.975950833333&de=66.6332&zoom=5&show_grid=1&show_constellation_lines=1&show_constellation_boundaries=1&show_const_names=1&show_galaxies=1&img_source=IMG_allhttp://www.wikisky.org/?ra=17.975950833333&de=66.6332&zoom=5&show_grid=1&show_constellation_lines=1&show_constellation_boundaries=1&show_const_names=1&show_galaxies=1&img_source=IMG_allhttp://www.wikisky.org/?ra=17.975950833333&de=66.6332&zoom=5&show_grid=1&show_constellation_lines=1&show_constellation_boundaries=1&show_const_names=1&show_galaxies=1&img_source=IMG_allhttp://www.wikisky.org/?ra=17.975950833333&de=66.6332&zoom=5&show_grid=1&show_constellation_lines=1&show_constellation_boundaries=1&show_const_names=1&show_galaxies=1&img_source=IMG_allhttp://www.wikisky.org/?ra=17.975950833333&de=66.6332&zoom=5&show_grid=1&show_constellation_lines=1&show_constellation_boundaries=1&show_const_names=1&show_galaxies=1&img_source=IMG_allhttp://www.wikisky.org/?ra=17.975950833333&de=66.6332&zoom=5&show_grid=1&show_constellation_lines=1&show_constellation_boundaries=1&show_const_names=1&show_galaxies=1&img_source=IMG_allhttp://www.wikisky.org/?ra=17.975950833333&de=66.6332&zoom=5&show_grid=1&show_constellation_lines=1&show_constellation_boundaries=1&show_const_names=1&show_galaxies=1&img_source=IMG_allhttp://www.wikisky.org/?ra=17.975950833333&de=66.6332&zoom=5&show_grid=1&show_constellation_lines=1&show_constellation_boundaries=1&show_const_names=1&show_galaxies=1&img_source=IMG_allhttp://www.wikisky.org/?ra=17.975950833333&de=66.6332&zoom=5&show_grid=1&show_constellation_lines=1&show_constellation_boundaries=1&show_const_names=1&show_galaxies=1&img_source=IMG_allhttp://en.wikipedia.org/wiki/New_General_Cataloguehttp://en.wikipedia.org/wiki/New_General_Cataloguehttp://en.wikipedia.org/wiki/New_General_Cataloguehttp://en.wikipedia.org/wiki/Planetary_nebulahttp://en.wikipedia.org/wiki/Planetary_nebulahttp://en.wikipedia.org/wiki/Planetary_nebulahttp://en.wikipedia.org/wiki/Draco_(constellation)http://en.wikipedia.org/wiki/Draco_(constellation)http://en.wikipedia.org/wiki/Draco_(constellation)http://en.wikipedia.org/wiki/Hubble_Space_Telescopehttp://en.wikipedia.org/wiki/Hubble_Space_Telescopehttp://en.wikipedia.org/wiki/Hubble_Space_Telescopehttp://en.wikipedia.org/wiki/William_Herschelhttp://en.wikipedia.org/wiki/William_Herschelhttp://en.wikipedia.org/wiki/William_Herschelhttp://en.wikipedia.org/wiki/Spectroscopyhttp://en.wikipedia.org/wiki/Spectroscopyhttp://en.wikipedia.org/wiki/Spectroscopyhttp://en.wikipedia.org/wiki/Amateur_astronomyhttp://en.wikipedia.org/wiki/Amateur_astronomyhttp://en.wikipedia.org/wiki/Amateur_astronomyhttp://en.wikipedia.org/wiki/William_Hugginshttp://en.wikipedia.org/wiki/William_Hugginshttp://en.wikipedia.org/wiki/Electromagnetic_spectrumhttp://en.wikipedia.org/wiki/Electromagnetic_spectrumhttp://en.wikipedia.org/wiki/Far-infraredhttp://en.wikipedia.org/wiki/Far-infraredhttp://en.wikipedia.org/wiki/Far-infraredhttp://en.wikipedia.org/wiki/X-rayshttp://en.wikipedia.org/wiki/X-rayshttp://en.wikipedia.org/wiki/X-rayshttp://en.wikipedia.org/wiki/Coronal_mass_ejectionhttp://en.wikipedia.org/wiki/Coronal_mass_ejectionhttp://en.wikipedia.org/wiki/Coronal_mass_ejectionhttp://en.wikipedia.org/wiki/Binary_system_(astronomy)http://en.wikipedia.org/wiki/Binary_system_(astronomy)http://en.wikipedia.org/wiki/Binary_system_(astronomy)http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#General_informationhttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#General_informationhttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#Observationshttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#Observationshttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#Infrared_observationshttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#Infrared_observationshttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#Optical_and_ultraviolet_observationshttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#Optical_and_ultraviolet_observationshttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#Optical_and_ultraviolet_observationshttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#Infrared_observationshttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#Observationshttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#General_informationhttp://en.wikipedia.org/wiki/Binary_system_(astronomy)http://en.wikipedia.org/wiki/Coronal_mass_ejectionhttp://en.wikipedia.org/wiki/X-rayshttp://en.wikipedia.org/wiki/Far-infraredhttp://en.wikipedia.org/wiki/Electromagnetic_spectrumhttp://en.wikipedia.org/wiki/William_Hugginshttp://en.wikipedia.org/wiki/Amateur_astronomyhttp://en.wikipedia.org/wiki/Spectroscopyhttp://en.wikipedia.org/wiki/William_Herschelhttp://en.wikipedia.org/wiki/Hubble_Space_Telescopehttp://en.wikipedia.org/wiki/Draco_(constellation)http://en.wikipedia.org/wiki/Planetary_nebulahttp://en.wikipedia.org/wiki/New_General_Cataloguehttp://www.wikisky.org/?ra=17.975950833333&de=66.6332&zoom=5&show_grid=1&show_constellation_lines=1&show_constellation_boundaries=1&show_const_names=1&show_galaxies=1&img_source=IMG_allhttp://en.wikipedia.org/wiki/Celestial_coordinate_systemhttp://en.wikipedia.org/wiki/Category:Lists_of_nebulaehttp://en.wikipedia.org/wiki/Planetary_nebulahttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/w/index.php?title=IC_4677&action=edit&redlink=1http://en.wikipedia.org/wiki/Index_Cataloguehttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-simbad-0http://en.wikipedia.org/wiki/New_General_Cataloguehttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-3http://en.wikipedia.org/wiki/Absolute_magnitudehttp://en.wikipedia.org/wiki/Absolute_magnitudehttp://en.wikipedia.org/wiki/Light_yearhttp://en.wikipedia.org/wiki/Light_yearhttp://en.wikipedia.org/wiki/Radius7/30/2019 Cat's Eye Nebula
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o 2.3 X-ray observations 3 Distance 4 Age 5 Composition 6 Kinematics and morphology 7 Open questions 8 Notes 9 References 10 Cited sources 11 External links
General information
NGC 6543 is a well-studied planetary nebula. It is relatively bright atmagnitude8.1,
and also has a highsurface brightness.[3]
It is situated atright ascension17h 58 m 33.4 sanddeclination+6637'59.
[4]Its high declination means it is easily observable from the
northern hemisphere, where historically most largetelescopeshave been situated.[3]
NGC 6543 is situated almost exactly in the direction of theNorth Ecliptic Pole.
While the bright inner nebula is rather smallthe major axis of the inner ellipse is 16.1
arcseconds, while the distance between the condensations is 24.7 arcseconds[5]it has
an extendedhaloof matter that the progenitor star ejected during itsred giantphase.
This halo extends over a diameter of about 300 arcseconds (5arcminutes)[4]
. The cat's
Eye nebula lies three thousand light-years from Earth.[6]
Observations show that the main body of the nebula has a density of about 5,000particles/cm and a temperature of about 7,0009,000K.
[7]The outer halo has a higher
temperature of about 15,000 K and a much lower density.[8]
The central star of NGC 6543 is anO7+[WR]type star, with a temperature of
approximately 80,000 K.[7]
It is approximately 10,000 times as luminous as the sun, and
its radius is about 0.65 times the solar value.Spectroscopic analysisshows that the star
is currently losing mass in a faststellar windat a rate of about 3.2107 solar masses per
yearabout 20 trilliontonsper second.[7]
The velocity of this wind is about 1900 km/s.
Calculations indicate that the central star currently weighs just over onesolar mass, but
theoretical evolutionary calculations imply that it had an initial mass of about 5 solar
masses.[9]
In 1994, Hubble first revealed NGC 6543's surprisingly intricate structures, including
concentric gas shells, jets of high-speed gas, and unusual shock-induced knots of gas.
Observations
The Nebula was discovered byWilliam Herschelon February 15, 1786, who likened its
appearance to a planetary disk. Cat's Eye was the first planetary nebula to be observed
with aspectroscope. It was done by the pioneerspectroscopistWilliam Hugginson
August 29, 1864.[10]Huggins' observations, which revealed that nebula's spectrum wasnon-continuous and made of a few bright lines, were the first indication that planetary
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nebulae consist of extremelyrarefiedgases.[3]
Since those early observations, NGC
6543 has been observed right across theelectromagnetic spectrum.
Infrared observations
Observations of NGC 6543 atfar-infraredwavelengths (about 60 m) reveal thepresence ofstellar dustat low temperatures. The dust is believed to have formed during
the last phases of the progenitor star's life. It absorbs light from the central star and re-
radiates it atinfraredwavelengths. The spectrum of the infrared dust emission implies
that the dust temperature is about 85 K, while the mass of the dust is estimated at
6.4 104 solar masses.[11]
Infrared emission also reveals the presence ofun-ionisedmaterial such asmolecular
hydrogen(H2) andargon. In many planetary nebulae, molecular emission is greatest at
larger distances from the star, where more material is un-ionised, but molecular
hydrogen emission in NGC 6543 seems to be bright at the inner edge of its outer halo.
This may be due toshock wavesexciting the H2 as ejecta moving at different speedscollide. The overall appearance of Cat's Eye Nebula in infrared (wavelengths 28 m) is
similar in visible light.[12]
Optical and ultraviolet observations
NGC 6543 has been extensively observed atultravioletandopticalwavelengths.
Spectroscopic observations at these wavelengths are used in abundance
determinations,[13]
while images at these wavelengths have been used to reveal the
intricate structure of the nebula.[14]
The Hubble Space Telescope image produced here is in false colour, designed to
highlight regions of high and lowionisation. Three images were taken, in filters
isolating the light emitted by singly ionisedhydrogenat 656.3nm, singly ionised
nitrogenat 658.4 nm and doubly ionisedoxygenat 500.7 nm. The images were
combined as red, green and blue channels respectively, although their true colours are
red, red and green. The image reveals two 'caps' of less ionised material at the edge of
the nebula.[15]
X-ray observations
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X-ray image of Nebula.
Recent observations atX-raywavelengths by theChandra X-ray Observatoryhave
revealed the presence of extremely hot gas within NGC 6543 with the temperature of
1.7 106
K.[16]
The image at the top of this article is a combination of optical images
from the Hubble Space Telescope with the Chandra X-ray images. It is thought that thevery hot gas results from the violent interaction of a fast stellar wind with material
previously ejected. This interaction has hollowed out the inner bubble of the nebula.[14]
Chandra observations have also revealed apoint sourceat the position of the central
star. The spectrum of this source extends to the hard part of the X-ray spectrum, to 0.5
1.0keV. The star with thephotospherictemperature of about 100,000 K would not be
expected to emit strongly in hard X-rays, and so their presence is something of a
mystery. It may suggest the presence of a high temperatureaccretion diskwithin a
binary starsystem.[17]
Distance
A long-standing problem in the study of planetary nebulae is that their distances are
generally not well known. Many methods for estimating distances to planetary nebulae
rely on making general assumptions, which may be very inaccurate for the object
concerned.[18]
In recent years, however, observations made using the Hubble Space Telescope have
allowed a new method of determining distances. All planetary nebulae are expanding,
and observations several years apart and with high enoughangular resolutionwill reveal
the growth of the nebula in the plane of the sky. This is typically very smallonly afew milliarcseconds a year or less.Spectroscopicobservations can reveal the velocity of
expansion of the nebula along the line of sight using theDoppler effect. Then,
comparing the angular expansion with the known expansion velocity, the distance to the
nebula can be calculated.[18]
Hubble Space Telescope observations of NGC 6543 several years apart have been used
to calculate its distance. Its angular expansion rate is 3.457 milliarcseconds per year,
while its expansion velocity along the line of sight has been found to be 16.4 km/s.
Combining these two results implies that NGC 6543 is 1001 269parsecs(31019
m),
or about 3300light-yearsaway from Earth.[19]
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, as
ejected material will be slowed as it encounters material ejected from the star at earlier
stages of its evolution, as well as theinterstellar medium.[19]
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Composition
Image of NGC 6543 processed to reveal the concentric rings surrounding the inner core.Also visible are the linear structures, possibly caused by precessing jets from a binary
central star system.
Like most astronomical objects, NGC 6543 consists mostly ofhydrogenandhelium,
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.[8]
Different studies generally find varying values for elemental abundances. This is often
becausespectrographsattached to telescopes do not collect all the light from objects
being observed, instead gathering light from a slit or smallaperture. Therefore, differentobservations may sample different parts of the nebula.
However, results for NGC 6543 broadly agree that, relative to hydrogen, the helium
abundance is about 0.12,carbonandnitrogenabundances are both about 3104
, and
theoxygenabundance is about 7104.[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 ofnucleosynthesisenriching the star's
atmosphere in heavy elements before it is ejected as a planetary nebula.[20]
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 discussedbelow.
[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 nebular 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.[5]
http://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Heliumhttp://en.wikipedia.org/wiki/Heliumhttp://en.wikipedia.org/wiki/Heliumhttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Wesson2-9http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Wesson2-9http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Wesson2-9http://en.wikipedia.org/wiki/Spectrographhttp://en.wikipedia.org/wiki/Spectrographhttp://en.wikipedia.org/wiki/Spectrographhttp://en.wikipedia.org/wiki/Aperturehttp://en.wikipedia.org/wiki/Aperturehttp://en.wikipedia.org/wiki/Aperturehttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Wesson3-14http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Wesson3-14http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Wesson3-14http://en.wikipedia.org/wiki/Nucleosynthesishttp://en.wikipedia.org/wiki/Nucleosynthesishttp://en.wikipedia.org/wiki/Nucleosynthesishttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-21http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-21http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-21http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Wesson3-14http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Wesson3-14http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Wesson3-14http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick1987-1-15http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick1987-1-15http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick1987-1-15http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Reedetal1999-3-6http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Reedetal1999-3-6http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Reedetal1999-3-6http://en.wikipedia.org/wiki/File:Catseye-big.jpghttp://en.wikipedia.org/wiki/File:Catseye-big.jpghttp://en.wikipedia.org/wiki/File:Catseye-big.jpghttp://en.wikipedia.org/wiki/File:Catseye-big.jpghttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Reedetal1999-3-6http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick1987-1-15http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Wesson3-14http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-21http://en.wikipedia.org/wiki/Nucleosynthesishttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Wesson3-14http://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Aperturehttp://en.wikipedia.org/wiki/Spectrographhttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Wesson2-9http://en.wikipedia.org/wiki/Heliumhttp://en.wikipedia.org/wiki/Hydrogen7/30/2019 Cat's Eye Nebula
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The structure of the bright portion of the nebula is primarily caused by the interaction of
a faststellar windbeing emitted by the central star with 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 star of the nebula may be abinary star. The existence
of anaccretion diskcaused by mass transfer between the two components of the system
may give rise topolar jets, which would interact with previously ejected material. Over
time, the direction of the polar jets would vary due toprecession.[21]
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 theasymptotic giant branchof theHertzsprung-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.[4]
The total mass of the
rings is about 0.1 solar masses.[22]The pulsations that formed the rings probably started15,000 years ago and ceased about 1,000 years ago, when the formation of the bright
central part began (see above).[23]
Further out, 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.[22]
Open questions
Photo taken by the Hubble Space Telescope in 1994
Despite intensive study, the Cat's Eye Nebula still holds many mysteries. The concentric
rings surrounding the inner nebula seem to have been ejected at intervals of from a few
hundred to a few thousand years, a timescale which is rather difficult to explain.
Thermal pulsations, which cause formation of planetary nebulae, are believed to take
place at intervals of tens of thousands of years, while smaller surface pulsations are
thought to occur at intervals of years to decades. A mechanism which would eject
material over the timescales required to form the concentric rings in the Cat's Eye
Nebula is not known yet.[23]
http://en.wikipedia.org/wiki/Stellar_windhttp://en.wikipedia.org/wiki/Stellar_windhttp://en.wikipedia.org/wiki/Stellar_windhttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick1987-1-15http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick1987-1-15http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick1987-1-15http://en.wikipedia.org/wiki/Binary_starhttp://en.wikipedia.org/wiki/Binary_starhttp://en.wikipedia.org/wiki/Binary_starhttp://en.wikipedia.org/wiki/Accretion_diskhttp://en.wikipedia.org/wiki/Accretion_diskhttp://en.wikipedia.org/wiki/Accretion_diskhttp://en.wikipedia.org/wiki/Polar_jethttp://en.wikipedia.org/wiki/Polar_jethttp://en.wikipedia.org/wiki/Polar_jethttp://en.wikipedia.org/wiki/Precessionhttp://en.wikipedia.org/wiki/Precessionhttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-22http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-22http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-22http://en.wikipedia.org/wiki/Asymptotic_giant_branchhttp://en.wikipedia.org/wiki/Asymptotic_giant_branchhttp://en.wikipedia.org/wiki/Asymptotic_giant_branchhttp://en.wikipedia.org/wiki/Hertzsprung-Russell_diagramhttp://en.wikipedia.org/wiki/Hertzsprung-Russell_diagramhttp://en.wikipedia.org/wiki/Hertzsprung-Russell_diagramhttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-1-5http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-1-5http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-1-5http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-2-23http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-2-23http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-2-23http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-3-24http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-3-24http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-3-24http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-2-23http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-2-23http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-2-23http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-3-24http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-3-24http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-3-24http://en.wikipedia.org/wiki/File:The_Cat's_Eye_Nebula_-_GPN-2000-000955.jpghttp://en.wikipedia.org/wiki/File:The_Cat's_Eye_Nebula_-_GPN-2000-000955.jpghttp://en.wikipedia.org/wiki/File:The_Cat's_Eye_Nebula_-_GPN-2000-000955.jpghttp://en.wikipedia.org/wiki/File:The_Cat's_Eye_Nebula_-_GPN-2000-000955.jpghttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-3-24http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-2-23http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-3-24http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-2-23http://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick2001-1-5http://en.wikipedia.org/wiki/Hertzsprung-Russell_diagramhttp://en.wikipedia.org/wiki/Asymptotic_giant_branchhttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-22http://en.wikipedia.org/wiki/Precessionhttp://en.wikipedia.org/wiki/Polar_jethttp://en.wikipedia.org/wiki/Accretion_diskhttp://en.wikipedia.org/wiki/Binary_starhttp://en.wikipedia.org/wiki/Cat%27s_Eye_Nebula#cite_note-Balick1987-1-15http://en.wikipedia.org/wiki/Stellar_wind7/30/2019 Cat's Eye Nebula
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The spectra of planetary nebulae consist ofemission linessuperimposed on a
continuum. The emission lines may be formed either bycollisional excitationofionsin
the nebula, or byrecombinationofelectronswith ions. Collisionally excited lines are
generally much stronger than recombination lines, and so have historically been used to
determine abundances. However, recent studies have found that abundances derived
from recombination lines seen in the spectrum of NGC 6543 are some three timeshigher than those derived from collisionally excited lines. The cause of this discrepancy
is probably related to spatial temperature fluctuations inside the nebula.[13]
Notes
1. ^Distance sin(diameter_angle / 2 ) = 0.2 ly. radius2. ^9.8B apparent magnitude5{log(1.0 0.3 kpc distance) 1} = 0.2+0.8
0.6B absolute magnitude
References1. ^abcdefg(SIMBAD 2006)2. ^ab(Reed et al. 1999)3. ^abc(Moore 2007)4. ^abc(Balick, Wilson & Hajian 2001, p. 354)5. ^ab(Reed et al. 1999, p. 2433)6. ^Nemiroff, Robert."The Cat's Eye Nebula From Hubble". NASA.
http://apod.nasa.gov/apod/ap070513.html. Retrieved october 26, 2011.
7. ^abc(Wesson & Liu 2004, pp. 1026, 1028)8. ^ab(Wesson & Liu 2004, p. 1029)9. ^(Bianchi, Cerrato & Grewing 1986)10. ^(kwok 2000, p. 1)11. ^(Klaas et al. 2006, p. 523)12. ^(Hora et al. 2004, p. 299)13. ^abcd(Wesson & Liu 2004, pp. 10261027, 10401041)14. ^abcd(Balick & Preston 1987, pp. 958, 961963)15. ^(Wesson & Liu 2004, pp. 10271031)16. ^(Chu et al. 2001)17. ^(Guerrero et al. 2001)18. ^ab(Reed et al. 1999, p. 2430)19. ^ab(Reed et al. 1999, pp. 24332438)20. ^(Hyung et al. 2000)21. ^(Miranda & Solf 1992)22. ^ab(Balick, Wilson & Hajian 2001, p. 358)23. ^ab(Balick, Wilson & Hajian 2001, pp. 359360)
Cited sources
Balick, Bruce; Preston, Heather L. (October 1987), "A wind-blown bubble model forNGC 6543",Astronomical Journal94: 958963,Bibcode1987AJ.....94..958B,doi:10.1086/114528
Balick, Bruce; Wilson, Jeanine; Hajian, Arsen R. (2001), "NGC 6543: The RingsAround the Cat's Eye",Astronomical Journal121 (1): 354,Bibcode
2001AJ....121..354B,doi:10.1086/318052
Bianchi, L.; Cerrato, S.; Grewing, M. (November 1986), "Mass loss from central starsof planetary nebulaethe nucleus of NGC 6543",Astronomy and Astrophysics169 (12): 227236,Bibcode1986A&A...169..227B
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Cat's Eye Nebula
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Chu, You-Hua; Guerrero, Martn A.; Gruendl, Robert A.; Williams, Rosa M.; Kaler,James B. (2001), "Chandra reveals the X-ray glint in the cat's eye",Astrophysical
Journal553 (1): L69L72,arXiv:astro-ph/0101444,Bibcode2001ApJ...553L..69C,doi:10.1086/320495
Guerrero, Martn A.; Chu, You-Hua; Gruendl, Robert A.; Williams, Rosa M.; Kaler,James B. (2001), "The Enigmatic X-Ray Point Sources at the Central Stars of NGC
6543 and NGC 7293",Astrophysical Journal553 (1): L55L58,arXiv:astro-ph/0104270,Bibcode2001ApJ...553L..55G,doi:10.1086/320509
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Planetary Nebulae",Astrophysical Journal Supplement Series154 (1): 296301,Bibcode2004ApJS..154..296H,doi:10.1086/422820
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Astronomical Society318 (1): 7791,Bibcode2000MNRAS.318...77H,doi:10.1046/j.1365-8711.2000.03642.x
Klaas, U.; Walker, S. J.; Mller, T. G.; Richards, P. J.; Schreiber, J. (2006), "Multi-aperture photometry of extended IR sources with ISOPHOT. I. The nature of extendedIR emission of planetary Nebulae",Astronomy and Astrophysics452 (2): 523535,Bibcode2006A&A...452..523K,doi:10.1051/0004-6361:20053245
Kwok, Sun(2000),"Chapter1: History and overview",The origin and evolution ofplanetary nebulae, Cambridge University Press, pp. 17,ISBN0-521-62313-8,http://books.google.com/?id=7NfqpZxO_o0C
Miranda, L. F.; Solf, J. (1992), "Long-slit spectroscopy of the planetary nebula NGC6543Collimated bipolar ejections from a precessing central source?",Astronomy andAstrophysics260 (12): 397410,Bibcode1992A&A...260..397M
Moore, S. L. (2007), "Observing the Cat's Eye Nebula",Journal of the BritishAstronomical Association117 (5): 279280,Bibcode2007JBAA..117R.279M
Reed, Darren S.; Balick, Bruce; Hajian, Arsen R.; Klayton, Tracy L.; Giovanardi,Stefano; Casertano, Stefano; Panagia, Nino; Terzian, Yervant (1999), "Hubble SpaceTelescope Measurements of the Expansion of NGC 6543: Parallax Distance and
Nebular Evolution",Astronomical Journal118 (5): 24302441,arXiv:astro-ph/9907313,Bibcode1999AJ....118.2430R,doi:10.1086/301091
SIMBAD(December 22, 2006),Results for Cat's Eye Nebula, SIMBAD, Centre deDonnes Astronomiques de Strasbourg,http://simbad.u-strasbg.fr/simbad/sim-
id?protocol=html&Ident=Cat's+Eye+Nebula
Wesson, R.; Liu, X.-W. (2004), "Physical conditions in the planetary nebula NGC6543",Monthly Notices of the Royal Astronomical Society351 (3): 10261042,Bibcode2004MNRAS.351.1026W,doi:10.1111/j.1365-2966.2004.07856.x
External links
Wikimedia Commons has media related to:Cat's Eye Nebula
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
o The Cat's Eye NebulaOctober 31, 1999o Halo of the Cat's Eye2010 May 9
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Cat's Eye Nebula
10/13
Hubble Probes the Complex History of a Dying StarHubbleSite article aboutthe Cat's Eye Nebula.
NGC6543 The Cats Eye Nebula Hubble's Color Toolbox: Cat's Eye Nebulaarticle showing image composite
process used to produce an image of the nebula
Cat's Eye Nebula onWikiSky:DSS2,SDSS,GALEX,IRAS,Hydrogen ,X-Ray,Astrophoto,Sky Map,Articles and images
v t e
Caldwell catalogue
List
C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 C19 C20 C21 C22 C23 C24 C25 C26 C27 C28 C29 C30 C31 C32 C33 C34
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