cat's eye nebula

7/30/2019 Cat's Eye Nebula

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Cat's Eye Nebula

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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_Telescope


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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/Radius


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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]
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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_wind


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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. âbcdefg(SIMBAD 2006)2. âb(Reed et al. 1999)3. âbc(Moore 2007)4. âbc(Balick, Wilson & Hajian 2001, p. 354)5. âb(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. âbc(Wesson & Liu 2004, pp. 1026, 1028)8. âb(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. âbcd(Wesson & Liu 2004, pp. 10261027, 10401041)14. âbcd(Balick & Preston 1987, pp. 958, 961963)15. ^(Wesson & Liu 2004, pp. 10271031)16. ^(Chu et al. 2001)17. ^(Guerrero et al. 2001)18. âb(Reed et al. 1999, p. 2430)19. âb(Reed et al. 1999, pp. 24332438)20. ^(Hyung et al. 2000)21. ^(Miranda & Solf 1992)22. âb(Balick, Wilson & Hajian 2001, p. 358)23. âb(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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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

Hora, Joseph L.; Latter, William B.; Allen, Lori E.; Marengo, Massimo; Deutsch,Lynne K.; Pipher, Judith L. (2004), "Infrared Array Camera (IRAC) Observations of

Planetary Nebulae",Astrophysical Journal Supplement Series154 (1): 296301,Bibcode2004ApJS..154..296H,doi:10.1086/422820

Hyung, S.; Aller, L. H.; Feibelman, W. A.; Lee, W. B.; de Koter, A. (2000), "Theoptical spectrum of the planetary nebula NGC 6543",Monthly Notices of the Royal

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

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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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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
http://hubblesite.org/newscenter/newsdesk/archive/releases/1995/01/http://www.dsi-astronomie.de/NGC6543.htmlhttp://www.dsi-astronomie.de/NGC6543.htmlhttp://hubblesite.org/sci.d.tech/behind_the_pictures/meaning_of_color/catseye.shtmlhttp://en.wikipedia.org/wiki/WikiSkyhttp://en.wikipedia.org/wiki/WikiSkyhttp://en.wikipedia.org/wiki/WikiSkyhttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=DSS2http://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=DSS2http://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=DSS2http://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=SDSShttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=SDSShttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=SDSShttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=GALEXhttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=GALEXhttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=GALEXhttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=IRAShttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=IRAShttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=IRAShttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=HALPHAhttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=HALPHAhttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=HALPHAhttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=RASShttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=RASShttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=RASShttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=RASShttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=IMG_allhttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=IMG_allhttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebula&img_source=IMG_allhttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebulahttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebulahttp://www.wikisky.org/?object=Cat%26%2339%3Bs+Eye+Nebulahttp://www.wikisky.org/starview?object=Cat%26%2339%3Bs+Eye+Nebulahttp://www.wikisky.org/starview?object=Cat%26%2339%3Bs+Eye+Nebulahttp://www.wikisky.org/starview?object=Cat%26%2339%3Bs+Eye+Nebulahttp://en.wikipedia.org/wiki/Template:Caldwell_cataloguehttp://en.wikipedia.org/wiki/Template:Caldwell_cataloguehttp://en.wikipedia.org/wiki/Template_talk:Caldwell_cataloguehttp://en.wikipedia.org/wiki/Template_talk:Caldwell_cataloguehttp://en.wikipedia.org/w/index.php?title=Template:Caldwell_catalogue&action=edithttp://en.wikipedia.org/w/index.php?title=Template:Caldwell_catalogue&action=edithttp://en.wikipedia.org/wiki/Caldwell_cataloguehttp://en.wikipedia.org/wiki/Caldwell_cataloguehttp://en.wikipedia.org/wiki/Caldwell_cataloguehttp://en.wikipedia.org/wiki/Caldwell_cataloguehttp://en.wikipedia.org/wiki/NGC_188http://en.wikipedia.org/wiki/NGC_188http://en.wikipedia.org/wiki/NGC_40http://en.wikipedia.org/wiki/NGC_40http://en.wikipedia.org/wiki/NGC_4236http://en.wikipedia.org/wiki/NGC_4236http://en.wikipedia.org/wiki/Iris_Nebulahttp://en.wikipedia.org/wiki/Iris_Nebulahttp://en.wikipedia.org/wiki/IC_342http://en.wikipedia.org/wiki/IC_342http://en.wikipedia.org/wiki/NGC_2403http://en.wikipedia.org/wiki/NGC_2403http://en.wikipedia.org/wiki/NGC_559http://en.wikipedia.org/wiki/NGC_559http://en.wikipedia.org/wiki/Cave_Nebulahttp://en.wikipedia.org/wiki/Cave_Nebulahttp://en.wikipedia.org/wiki/NGC_663http://en.wikipedia.org/wiki/NGC_663http://en.wikipedia.org/wiki/NGC_7635http:/

cat's eye nebula

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