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TOPIC: Helix nebula


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Title: Herschel imaging of the dust in the Helix Nebula (NGC 7293)
Author: G.C. Van de Steene, P. A. M. van Hoof, K. M. Exter, M. J. Barlow, J. Cernicharo, M. Etxaluze, W. K. Gear, J. R. Goicoechea, H. L. Gomez, M. A. T. Groenewegen, P. C. Hargrave, R. J. Ivison, S. J. Leeks, T. L. Lim, M. Matsuura, G. Olofsson, E. T. Polehampton, B. M. Swinyard, T. Ueta, H. Van Winckel, C. Waelkens, R. Wesson

In our series of papers presenting the Herschel imaging of evolved planetary nebulae, we present images of the dust distribution in the Helix nebula (NGC 7293). Images at 70, 160, 250, 350, and 500 micron were obtained with the PACS and SPIRE instruments on board the Herschel satellite. The broadband maps show the dust distribution over the main Helix nebula to be clumpy and predominantly present in the barrel wall. We determined the spectral energy distribution of the main nebula in a consistent way using Herschel, IRAS, and Planck flux values. The emissivity index of 0.99 0.09, in combination with the carbon rich molecular chemistry of the nebula, indicates that the dust consists mainly of amorphous carbon. The dust excess emission from the central star disk is detected at 70 micron and the flux measurement agree with previous measurement. We present the temperature and dust column density maps. The total dust mass across the Helix nebula (without its halo) is determined to be 0.0035 solar mass at a distance of 216 pc. The temperature map shows dust temperatures between 22 and 42 K, which is similar to the kinetic temperature of the molecular gas, strengthening the fact that the dust and gas co-exist in high density clumps. Archived images are used to compare the location of the dust emission in the far infrared (Herschel) with the ionized (GALEX, Hbeta) and molecular hydrogen component. The different emission components are consistent with the Helix consisting of a thick walled barrel-like structure inclined to the line of sight. The radiation field decreases rapidly through the barrel wall.

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Image taken with Faulkes Telescope North operated by Las Cumbres Observatory Global Telescope Network
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The Helix Nebula: Bigger in Death than Life

A dying star is refusing to go quietly into the night, as seen in this combined infrared and ultraviolet view from NASA's Spitzer Space Telescope and the Galaxy Evolution Explorer (GALEX), which NASA has lent to the California Institute of Technology in Pasadena. In death, the star's dusty outer layers are unravelling into space, glowing from the intense ultraviolet radiation being pumped out by the hot stellar core.
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Title: Discovery of a halo around the Helix Nebula NGC 7293 in the WISE all-sky survey
Authors: Yong Zhang, Chih-Hao Hsia, Sun Kwok

We report the discovery of an extended halo (40' in diameter) around the planetary nebula NGC7293 (the Helix Nebula) observed in 12micron band from the Wide-field Infrared Survey Explorer all-sky survey. The mid-infrared halo has an axisymmetric structure with a sharp boundary to the northeast and a more diffuse boundary to the southwest, suggesting an interaction between the stellar wind and the interstellar medium (ISM). The symmetry axis of the halo is well aligned with that of a northeast arc, suggesting that the two structures are physically associated. We have attempted to fit the observed geometry with a model of a moving steady-state stellar wind interacting with the ISM. Possible combinations of the ISM density and the stellar velocity are derived from these fittings. The discrepancies between the model and the observations suggest that the stellar mass loss has a more complicated history, including possible time and angle dependences.

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The Helix in New Colours

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ESO's VISTA telescope, at the Paranal Observatory in Chile, has captured a striking new image of the Helix Nebula. This picture, taken in infrared light, reveals strands of cold nebular gas that are invisible in images taken in visible light, as well as bringing to light a rich background of stars and galaxies.

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VISTA Views Helix Nebula in Infrared

A new photo of the Helix Nebula, located about 700 light-years away in the constellation of Aquarius, was captured by the European Southern Observatorys VISTA telescope in Chile.
Seen in infrared light, the planetary nebula is composed of dust and cold molecular hydrogen gas, forming a beautiful pattern around a hot star, which appears as a tiny blue dot in the center of the image.

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ESO- Zooming into the Helix Nebula.



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A new image of a gaseous space nebula reveals tens of thousands of giant comet-like knots raining down in a star-spangled cosmic fireworks display.
The gorgeous photograph by Japan's Subaru Telescope in Hawaii, released this week, reveals fresh details about the aftermath of a star's death, but the origin of the knots remains a mystery.
Each knot is about five times the size of the orbit of Pluto in our solar system.
The relatively nearby scene -- just 710 light-years away -- is a close-up of small section in the Helix Nebula, also named NGC 7293. It's within our Milky Way Galaxy.

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NGC 7293
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A deep new image of the magnificent Helix planetary nebula has been obtained using the Wide Field Imager at ESO's La Silla Observatory. The image shows a rich background of distant galaxies, usually not seen in other images of this object.
The Helix Nebula, NGC 7293, lies about 700 light-years away in the constellation of Aquarius (the Water Bearer). It is one of the closest and most spectacular examples of a planetary nebula. These exotic objects have nothing to do with planets, but are the final blooming of Sun-like stars before their retirement as white dwarfs. Shells of gas are blown off from a stars surface, often in intricate and beautiful patterns, and shine under the harsh ultraviolet radiation from the faint, but very hot, central star. The main ring of the Helix Nebula is about two light-years across or half the distance between the Sun and its closest stellar neighbour.

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Title: A Debris Disk around the Central Star of the Helix Nebula?
Authors: Kate Y. L. Su (1), Y.-H. Chu (2), G. H. Rieke (1), P. J. Huggins (3), R. Gruendl (2), R. Napiwotzki (4), T. Rauch (5), W. B. Latter (6), K. Volk (7) ((1) Univ. of Arizona, (2) UIUC, (3) New York Univ, (4) Univ. of Hertfordshire, UK, (5) Univ. of Tubingen, Germany, (6) Hersche Science Centre, (7) Gemini Obs.)

Excess emission from a point-like source coincident with the central star of the Helix Nebula is detected with Spitzer at 8, 24, and 70 um. At 24 um, the central source is superposed on an extended diffuse emission region. While the [OIV] 25.89 um line contributes to the diffuse emission, a 10-35 um spectrum of the central source shows a strong thermal continuum. The excess emission from the star most likely originates from a dust disk with blackbody temperatures of 90--130 K. Assuming a simple optically thin debris disk model, the dust is distributed in a ring between ~35 and ~150 AU from the central star, possibly arising from collisions of Kuiper-Belt-like Objects or the break-up of comets from an Oort-like cloud that have survived from the post-main-sequence evolution of the central star.

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