240514 - C6 "Cat's Eye" nebula
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click image to enlarge
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ASTRO:
type=Planetary Nebula const=Draco mag=9.8 dist~3300 ly size~6 ly IMAGE: location=EB Driveway BrtlCls=4 moon=45% WxCr exposure=outer shell> CMOS OSC: 42x300s (3.5h), G100 central core > CMOS OSC: 15x5s (1.3m), G100 EQUIPMENT: camera=ZWO ASI2600MC-Pro optics=ES102 w24mmEP 1.7x prjctn, F(eff)=1238mm, f/12.1 filter=Optolong L-eXtreme Duo NB mount=Celestron AVX guiding=Orion 60x240mm, ZWO ASi224MC SOFTWARE: acquisition=Stellarium, APT, PHD2, processing=PixInsight (RCAstro), Photoshop (Lumenzia), LrC |
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To some it looks like a cat's eye. To others, perhaps more like a giant cosmic sea shell. The Cat's Eye Nebula carries the scientific identifier Caldwell 6 (C6 for short), being included in the Caldwell catalog of astronomical objects first published in 1982 by British Astronomer, Sir Patrick Caldwell-Moore. Caldwell's catalog consists of 109 star clusters, nebulae, and galaxies for observation by amateur astronomers, and which, as claimed by Caldwell-Moore, was "intended as a [non-duplicative and] complement to the Messier catalogue". Because Charles Messier recorded all of his famous catalog's entries from locations in France which is a northern latitude location, it does not contain many of the prominent objects we know today to be visible only from latitudes extending to the south from Earth's equator. Caldwell's catalog includes many of these southern objects. His list was published again in Sky & Telescope in December 1995.
The Cat's Eye is also catalogued as NGC 6543, and is one of the brightest and most highly detailed planetary nebula ("PN") known. It is composed of gas expelled by the central progenitor star near its end of life, during its red giant phase of stellar evolution. This nebula's dying central star is believed to have produced the outer circular concentric shell by shrugging off its outer layer in a single early convulsion; but when magnified, the central core reveals further pulsations of a beautiful, complex and symmetric structure that is not yet fully understood. Through blended composite images from the NASA/ESA Hubble and Chandra X-Ray Space Telescopes, the beautiful complexity of the object's central core is fully revealed.
The entirety of the outlying nebula spans appx 6 light-years across. By gazing into the Cat's Eye, humanity may well be seeing the fate of our Sun, destined to enter its own planetary nebula phase of evolution ...in about 5 billion years. The Cat's Eye was discovered by William Herschel in 1786. But it wasn't until 1846 that this optical wonder became the first planetary nebula to reveal its composition thru study of its electromagnetic (EM) emissions. In 1864, an early pioneer in the sub-study of astronomical spectroscopy, English astronomer William Huggins was the first to demonstrate that planetary nebulae are gaseous and not stellar in nature.
Today, the Cat's Eye is a well-studied object that has been intricately analyzed in multiple EM wavelengths ranging from radio to X-ray. Studies show the nebulosity near the center of the outlying cloud has an average temperature between 7000° and 9000° K, with densities averaging about 5000 particles per cubic centimeter; but the halo of the central core itself has an even higher temperature around 15,000° K, but surprisingly with much lower density. Outward velocity of the fast stellar wind has been measured at an astounding 1900 km/s. Equally amazing, spectroscopic analysis shows the current rate of loss of mass is 20 trillion tons per second.
At 300 mm aperture (~12"), observers find the core of the Cat's Eye begins to visually reveal its complex structure. ...Beginning at low magnification of about 26x, it can be slightly distinguished from a bright star. With increasing magnification, the diameter and richness of detail in the core increases. The very bright central star can best be seen at about 120x, and above that the structure of the nebula core becomes apparent. The core can best be seen at high magnification with a high-contrast filter, but its visibility is heavily dependent on a calm atmosphere. At 500x the core shows an appearance that resembles that of a pretzel; a cat's eye can also be interpreted.
Imagers find that capturing the faint outlying nebula cloud while simultaneously catching some of the detail in the very bright core region is extremely challenging. As was done in the image presented here, most imagers will use High Dynamic Range ("HDR") techniques to blend composite images captured at varying exposure rates.
The Cat's Eye is also catalogued as NGC 6543, and is one of the brightest and most highly detailed planetary nebula ("PN") known. It is composed of gas expelled by the central progenitor star near its end of life, during its red giant phase of stellar evolution. This nebula's dying central star is believed to have produced the outer circular concentric shell by shrugging off its outer layer in a single early convulsion; but when magnified, the central core reveals further pulsations of a beautiful, complex and symmetric structure that is not yet fully understood. Through blended composite images from the NASA/ESA Hubble and Chandra X-Ray Space Telescopes, the beautiful complexity of the object's central core is fully revealed.
The entirety of the outlying nebula spans appx 6 light-years across. By gazing into the Cat's Eye, humanity may well be seeing the fate of our Sun, destined to enter its own planetary nebula phase of evolution ...in about 5 billion years. The Cat's Eye was discovered by William Herschel in 1786. But it wasn't until 1846 that this optical wonder became the first planetary nebula to reveal its composition thru study of its electromagnetic (EM) emissions. In 1864, an early pioneer in the sub-study of astronomical spectroscopy, English astronomer William Huggins was the first to demonstrate that planetary nebulae are gaseous and not stellar in nature.
Today, the Cat's Eye is a well-studied object that has been intricately analyzed in multiple EM wavelengths ranging from radio to X-ray. Studies show the nebulosity near the center of the outlying cloud has an average temperature between 7000° and 9000° K, with densities averaging about 5000 particles per cubic centimeter; but the halo of the central core itself has an even higher temperature around 15,000° K, but surprisingly with much lower density. Outward velocity of the fast stellar wind has been measured at an astounding 1900 km/s. Equally amazing, spectroscopic analysis shows the current rate of loss of mass is 20 trillion tons per second.
At 300 mm aperture (~12"), observers find the core of the Cat's Eye begins to visually reveal its complex structure. ...Beginning at low magnification of about 26x, it can be slightly distinguished from a bright star. With increasing magnification, the diameter and richness of detail in the core increases. The very bright central star can best be seen at about 120x, and above that the structure of the nebula core becomes apparent. The core can best be seen at high magnification with a high-contrast filter, but its visibility is heavily dependent on a calm atmosphere. At 500x the core shows an appearance that resembles that of a pretzel; a cat's eye can also be interpreted.
Imagers find that capturing the faint outlying nebula cloud while simultaneously catching some of the detail in the very bright core region is extremely challenging. As was done in the image presented here, most imagers will use High Dynamic Range ("HDR") techniques to blend composite images captured at varying exposure rates.