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Messier 57
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The Ring nebula

Picture 834_PROCESSED

Untracked tripod capture, 10 seconds, ISO 1600, f5.6

Canon EOS 350D

Clear sky. Bortle 5.5



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NGC 6720
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The Ring nebula (Messier 57, NGC 6720) located between Beta and Gamma Lyrae in the constellation of Lyra. 

Picture 015 
Date 17.05.15 

14 x 4 second stack captured with an 8" F5 Newtonian reflector on an EQ5 mount.



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RE: Ring nebula
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EOTS: A guide to the Ring Nebula M57

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The ring nebula in Lyra.

Picture 014 

Reprocessed  24 x 10 second cropped stack using Registack V6 captured with a 8" f5 reflector and Canon EOS 350D. 

Motorised EQ5 Mount, prime focus

Clear sky, Brortle 5.



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The ring nebula in Lyra (upper right). The brightest star in main image is HD 176051.

Picture 016Picture 016SM
Date 09.04.15 Cropped view


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The central white dwarf star of the Ring Nebula was discovered on September 1, 1886
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NASA's Hubble Space Telescope Reveals the Ring Nebula's True Shape

hs-2013-13-b-web.jpg

The distinctive shape of the Ring Nebula, the glowing shroud around a dying Sun-like star, makes it a popular celestial object that appears in many astronomy books. New observations of the Ring Nebula by NASA's Hubble Space Telescope, however, reveal a new twist on an iconic nebula.
The Hubble images offer the best view yet of the nebula, revealing a complex structure. The observations have allowed astronomers to construct the most precise three-dimensional model of the glowing gas shroud, called a planetary nebula. Based on the new observations, the Hubble research team suggests that the ring wraps around a blue football-shaped structure that protrudes out of opposite sides of the ring. The nebula is tilted toward Earth so that astronomers see the ring face-on.

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Title: Probing the Mass and Structure of the Ring Nebula in Lyra with SOFIA/GREAT Observations of the [CII] 158 micron line
Authors: R. Sahai, M. R. Morris, M. W. Werner, R. Güsten, H. Wiesemeyer, G. Sandell

We have obtained new velocity-resolved spectra of the [CII] 158 micron line towards the Ring Nebula in Lyra (NGC 6720), one of the best-studied planetary nebulae, in order to probe its controversial 3-dimensional structure and to estimate the mass of circumstellar material in this object. We used the Terahertz receiver GREAT aboard the SOFIA airborne telescope to obtain the [CII] spectra at eight locations within and outside the bright optical ring of NGC 6720. Emission was detected at all positions except for the most distant position along the nebula's minor axis, and generally covers a broad velocity range, ~50 km/s (FWZI), except at a position along the major axis located just outside the optical ring, where it is significantly narrower (~25 km/s). The one narrow spectrum appears to be probing circumstellar material lying outside the main nebular shell that has not been accelerated by past fast wind episodes from the central star, and therefore most likely comes from equatorial and/or low-latitude regions of this bipolar nebula. Along lines-of-sight passing within about 10 arcsec of the nebular center, the CII column density is a factor 46 higher than the CO column density. The total mass of gas associated with the [CII] emission inside a circular region of diameter 87.5 arcsec is at least 0.11 solar masses. A significant amount of [CII] flux arises from a photodissociation region immediately outside the bright optical ring, where we find a CII to CO ratio of 6.5, lower than that seen towards the central region. Comparing our data with lower-quality CI spectra, which indicate similarly large CI/CO ratios in NGC 6720, we conclude that the bulk of elemental carbon in NGC 6720 is divided roughly equally between CII and CI, and that the emissions from these species are far more robust tracers of circumstellar material than CO in this object and other evolved planetary nebulae.

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Messier 57
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Messier 57 (M57) planetary nebula, also known as the "Ring Nebula", is often regarded as the prototype of a planetary nebula. Observations have confirmed that it is, most probably, actually a ring (torus) of bright light-emitting material surrounding its central star, and not a spherical (or ellipsoidal) shell.
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The Ring Nebula in Lyra

The Ring Nebula is in the northern constellation of Lyra. It was discovered in 1779 by Antoine Darquier de Pellepoix and by Charles Messier. It is included in the catalogue of diffuse objects of this second astronomer, with number 57. This nebula is placed at 2300 light-years from Earth. It seems to have begun to form 2000 years ago and it is expanding at a velocity of 20-30 km per second. The surface temperature of the central white dwarf is about 120 000 degrees Celsius.
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