سحابی هلیکس

معنی کلمه سحابی هلیکس

معنی واژه سحابی هلیکس

معنیسحابی هلیکس(به انگلیسی: Helix Nebula)، یا NGC 7293، یک سحابی سیاره‌ای در صورت فلکی دلو است که توسط کارل لودیگ هاردینگ و در سال ۱۸۲۴ کشف شد.این سحابی یکی از نزدیکترین و درخشان‌ترین سحابی‌های حلقوی است.

محتویات
منابع

ویکی‌پدیای انگلیسی:
↑ ۱٫۰ ۱٫۱ ۱٫۲ ۱٫۳ . Results for Helix Nebula ed. Retrieved on 2006-12-07.
↑ ۲٫۰ ۲٫۱ ODell, C. R.; McCullough, Peter R.; Meixner, Margaret. The Astronomical Journal 128, no. 5 (2004): 2339–2356.
↑ Hora, Joseph L.; Latter, William B.; Smith, Howard A.; Marengo, Massimo. The Astrophysical Journal 652, no. 1 (2006): 426–441.
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سحابی حلقوی
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در ویکی‌انبار پرونده‌هایی دربارهٔ سحابی هلیکس موجود است.
SEDS: NGC 7293, the Helix Nebula
NightSkyInfo.com – NGC 7293, the Helix Nebula
سحابی هلیکسدر ویکی‌آسمان: DSS2, SDSS, مادون قرمز, هیدروژن آلفا, پرتو ایکس, تصاویر نجومی, نقشه آسمان, مقالات و تصاویر
مختصات: ۲۲h ۲۹m ۳۸٫۵۵s -۲۰° ۵۰′ ۱۳٫۶″

رده‌های صفحه: اجرام ان‌جی‌سی سحابی‌هاسحابی‌های سیاره‌ای صورت فلکی دلو
قس عربی
The Helix Nebula (also known as The Helix, NGC 7293, or Caldwell 63) is a large planetary nebula (PN) located in the constellation Aquarius. Discovered by Karl Ludwig Harding, probably before 1824, this object is one of the closest to the Earth of all the bright planetary nebulae. The estimated distance is about 215 parsecs or 700 light-years. It is similar in appearance to the Ring Nebula, whose size, age, and physical characteristics are similar to the Dumbbell Nebula, varying only in its relative proximity and the appearance from the equatorial viewing angle. The Helix has often been referred to as the Eye of God on the Internet, since about 2003.
Contents
General information

The Helix Nebula is an example of a planetary nebula, or planetary formed at the end of a stars evolution. Gases from the star in the surrounding space appear, from our vantage point, as if we are looking down a helix structure. The remnant central stellar core, known as a planetary nebula nucleus or PNN, is destined to become a white dwarf star. The observed glow of the central star is so energetic that it causes the previously expelled gases to brightly fluoresce.
The Helix Nebula in the constellation of Aquarius lies about 700 light-years away, spanning about 0.8 parsec or 2.5 light-years. Recent images by the Hubble Space Telescope of the Helix Nebula are a composite of newly released images from the ACS instrument and the wide-angle images from the Mosaic Camera on the WIYN 0.9-metre telescope at Kitt Peak National Observatory.
Currently, the age is estimated to be 10,600+2,300
−1,200 years, based solely upon a measured expansion rate of 31 km·s−1.
Structure

The Helix Nebula is thought to be shaped like a prolate spheroid with strong density concentrations toward the filled disk along the equatorial plane, whose major axis is inclined about 21° to 37° from our vantage point. The size of the inner disk is 8×19 arcmin in diameter (0.52 pc); the outer torus is 12×22 arcmin in diameter (0.77 pc); and the outer-most ring is about 25 arcmin in diameter (1.76 pc). We see the outer-most ring as flattened on one side due to its colliding with the ambient interstellar medium.
Expansion of the whole planetary nebula structure is estimated to have occurred in the last 6,560 years, and 12,100 years for the inner diskneeded. Spectroscopically, the outer rings expansion rate is 40 km·s−1, and about 32 km·s−1 for the inner disk.


This zoom sequence starts with a wide-field view of the rather empty region of sky around the constellation of Aquarius.


This video compares a new view of the Helix Nebula acquired with the VISTA telescope in infrared light with the more familiar view in visible light from the MPG/ESO 2.2-metre telescope at ESOs La Silla Observatory.

NGC7293 (2004)



Infrared image of the Helix Nebula, taken by the Spitzer space telescope, 2007


Knots


NGC 7293 taken by VISTA.
The Helix Nebula was the first planetary nebula discovered to contain cometary knots. Its main ring contains knots of nebulosity, which have now been detected in many nearby planetaries. These knots are highly radially symmetric (from the PNN) and are described as "cometary", each containing bright cusps (local photoionization fronts) and tails. All extend away from the PNN in a radial direction. Excluding the tails, they are (very approximately) the size of the Solar system, while each of the cusp knots are optically thick due to Lyc photons from the (PNN). There are more than 20,000 cometary knots estimated to be in the Helix Nebula.
The excitation temperature varies across the Helix nebula. The rotational-vibrational temperature ranges from 1800 K in a cometary knot located in the inner region of the nebula are about 2.5′ (arcmin) from the central PNN, calculated at about 900 K in the outer region at the distance of 5.6′.
See also

New General Catalogue (NGC)
Notes

Footnotes
^ average(207+46
−24, 219+27
−21) = ((207 + 219) / 2) +((462 + 402)0.5 / 2)
−((242 + 212)0.5 / 2) = 213+30
−16
^ 13.5 apparent magnitude - 5 * (log10(242 pc distance) - 1) = 6.58 absolute magnitude
Citations
^ a b c d "SIMBAD Astronomical Database". Results for Helix Nebula. Retrieved 2006-12-07.
^ a b c d e ODell, C. R.; Balick, B.; Hajian, A. R.; Henney, W. J.; Burkert, A. (2002). "Knots in Nearby Planetary Nebulae". The Astronomical Journal 123 (6): 3329–3347. Bibcode 2002AJ....123.3329O. DOI:10.1086/340726.
^ a b Harris, Hugh C.; Dahn, Conard C.; Canzian, Blaise; Guetter, Harry H.; Leggett, S. K.; Levine, Stephen E.; Luginbuhl, Christian B.; Monet, Alice K. B.; Monet, David G.; Pier, Jeffrey R.; Stone, Ronald C.; Tilleman, Trudy; Vrba, Frederick J.; Walker, Richard L. (February 2007). "Trigonometric Parallaxes of Central Stars of Planetary Nebulae". The Astronomical Journal 133 (2): 631–638. arXiv:astro-ph/0611543. Bibcode 2007AJ....133..631H. DOI:10.1086/510348.
^ a b c d Matsuura, M.; Speck, A. K.; Smith, M. D.; Zijlstra, A. A.; Viti, S.; Lowe, K. T. E.; Redman, M.; Wareing, C. J.; Lagadec, E. (December 2007). "VLT/near-infrared integral field spectrometer observations of molecular hydrogen lines in the knots of the planetary nebula NGC 7293 (the Helix Nebula)". Monthly Notices of the Royal Astronomical Society 382 (4): 1447–1459. Bibcode 2007MNRAS.382.1447M. DOI:10.1111/j.1365-2966.2007.12496.x.
^ a b c ODell, C. R.; McCullough, Peter R.; Meixner, Margaret (2004). "Unraveling the Helix Nebula: Its Structure and Knots". The Astronomical Journal 128 (5): 2339–2356. arXiv:astro-ph/0407556. Bibcode 2004AJ....128.2339O. DOI:10.1086/424621.
^ OMeara, Stephen James (2002). The Caldwell Objects. Cambridge University Press. ISBN 0-521-82796-5.
^ Hora, Joseph L.; Latter, William B.; Smith, Howard A.; Marengo, Massimo (2006). "Infrared Observations of the Helix Planetary Nebula". The Astrophysical Journal 652 (1): 426–441. arXiv:astro-ph/0607541. Bibcode 2006ApJ...652..426H. DOI:10.1086/507944.
^ "Urban Legends Reference Pages". The Eye of God. Retrieved 2007-07-16.
^ {{Cite journal
^
^ Odell, C. R.; Balick, B.; Hajian, A. R.; Henney, W. J.; Burkert, A. (2003). "Knots in Planetary Nebulae". Winds, Bubbles, and Explosions: a conference to honor John Dyson, Pátzcuaro, Michoacán, México, September 9–13, 2002 (Eds. S. J. Arthur & W. J. Henney) Revista Mexicana de Astronomía y Astrofísica (Serie de Conferencias) ( 15: 29–33. Bibcode 2003RMxAC..15...29O.
External links

Wikimedia Commons has media related to: Helix Nebula
NASA APOD – May 10, 2003 NGC 7293: The Helix Nebula
SEDS: NGC 7293, the Helix Nebula
NightSkyInfo.com – NGC 7293, the Helix Nebula
Snopes.com; Helix Eye of God Urban Legend
The Helix Nebula on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
Coordinates: 22h 29m 38.55s, −20° 50′ 13.6″
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 C35 C36 C37 C38 C39 C40 C41 C42 C43 C44 C45 C46 C47 C48 C49 C50 C51 C52 C53 C54 C55 C56 C57 C58 C59 C60 C61 C62 C63 C64 C65 C66 C67 C68 C69 C70 C71 C72 C73 C74 C75 C76 C77 C78 C79 C80 C81 C82 C83 C84 C85 C86 C87 C88 C89 C90 C91 C92 C93 C94 C95 C96 C97 C98 C99 C100 C101 C102 C103 C104 C105 C106 C107 C108 C109
See also
Messier Catalogue Catalogue of Nebulae General Catalogue of Nebulae and Clusters New General Catalogue Index Catalogue Revised New General Catalogue Herschel 400 Catalogue
Book:Caldwell catalogue Category:Caldwell objects Portal:Astronomy Commons:Caldwell objects
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Categories: Aquarius (constellation)Caldwell objectsNGC objectsPlanetary nebulae
عربیسديم الحلزون