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Post Info TOPIC: The veil nebula
Blobrana


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NGC 6960
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The Veil Nebula (also NGC 6960, NGC 6992, NGC 6995, NGC 6974, NGC 6979, IC 1340, Caldwell 33/34, Witch's Broom Nebula and Cygnus Loop) is a magnitude +7.0 supernova remnant located 1470 light-years away in the constellation Cygnus.

The supernova remnant was discovered by the German-British astronomer William Herschel using a 47.5 cm (18.7 inch) f/13 speculum reflecting telescope at an old hunting lodge in Datchet on the 5th September 1784. 

Right Ascension 20h 45m 38.0s, Declination +30° 42' 30"

William Herschel described the western end of the nebula as "Extended; passes thro' 52 Cygni... near 2 degree in length", and described the eastern end as "Branching nebulosity... The following part divides into several streams uniting again towards the south."
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Blobrana


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Cygnus Loop
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A Panoramic Loop in Cygnus

cygloop-th.jpg

As an end of the year finale, the National Optical Astronomy Observatory (NOAO) and WIYN partners offer this new wide-field image of the Cygnus loop. Three degrees on a side, this image covers an area of the sky about 45 times that of the full moon. But it does so without sacrificing high resolution. The image is over 600 million pixels in size, making it one of the largest astronomical images ever made. 

The Cygnus Loop is a large supernova remnant: the gaseous remains of a massive star that exploded long ago. It is located about 1,500 light-years from Earth in the direction of the constellation Cygnus, the Swan. Astronomers estimate the supernova explosion that produced the nebula occurred between 5,000 to 10,000 years ago. First noted in 1784 by William Herschel, it is so large that its many parts have been catalogued as separate objects, including NGC 6992, NGC 6995 and IC 1340 along the eastern (left) side of the image, NGC 6974 and NGC 6979 near the top-center, and the Veil Nebula (NGC 6960) and Pickering's Triangle along the western (right) edge. The bright star near the western edge of the image, known as 52 Cygnus, is not associated with the supernova.

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Blobrana


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Cygnus Loop nebula
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glx2012-01r_img01_Sm.jpg

Wispy tendrils of hot dust and gas glow brightly in this ultraviolet image of the Cygnus Loop nebula, taken by NASA's Galaxy Evolution Explorer. The nebula lies about 1,500 light-years away, and is a supernova remnant, left over from a massive stellar explosion that occurred between 5,000 to 8,000 years ago.

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Blobrana


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Cygnus Loop Supernova Remnant
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Title: Fermi Large Area Telescope Observations of the Cygnus Loop Supernova Remnant
Authors: H. Katagiri, L. Tibaldo, J. Ballet, F. Giordano, I. A. Grenier, T. A. Porter, M. Roth, O. Tibolla, Y. Uchiyama, R. Yamazaki

We present an analysis of the gamma-ray measurements by the Large Area Telescope(LAT) onboard the Fermi Gamma-ray Space Telescope in the region of the supernova remnant(SNR) Cygnus Loop(G74.0-8.5). We detect significant gamma-ray emission associated with the SNR in the energy band 0.2--100 GeV. The gamma-ray spectrum shows a break in the range 2--3 GeV. The gamma-ray luminosity is ~1 x 10^{33}erg s^{-1} between 1--100 GeV, much lower than those of other GeV-emitting SNRs. The morphology is best represented by a ring shape, with inner/outer radii 0.7° ±0.1° and 1.6° ±0.1°. Given the association among X-ray rims, \halpha filaments and gamma-ray emission, we argue that gamma rays originate in interactions between particles accelerated in the SNR and interstellar gas or radiation fields adjacent to the shock regions. The decay of neutral pions produced in nucleon-nucleon interactions between accelerated hadrons and interstellar gas provides a reasonable explanation for the gamma-ray spectrum.

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Google earth file: Cygnus highlights.kmz (8kb, kmz)



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Blobrana


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RE: The veil nebula
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There are three main visual components:

  • The Western Veil (also known as Caldwell 34), consisting of NGC 6960 (the "Witch's Broom") near the foreground star 52 Cygni;
  • The Eastern Veil (also known as Caldwell 33), whose brightest area is NGC 6992, trailing off farther south into NGC 6995 and IC 1340; and
  • Pickering's Triangle (or Pickering's Triangular Wisp), brightest at the north central edge of the loop, but visible in photographs continuing toward the central area of the loop.

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Blobrana


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Cygnus Loop XA Region
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Title: Chandra Imaging and Spectroscopy of the Eastern XA Region of the Cygnus Loop Supernova Remnant
Authors: Randall L. McEntaffer, Thomas Brantseg

The XA region of the Cygnus Loop is a bright knot of X-ray emission on the eastern edge of the supernova remnant resulting from the interaction of the supernova blast wave with density enhancements at the edge of a precursor formed cavity. To study the nature and origin of the X-ray emission we use high spatial resolution images from Chandra. Our goal is to probe the density of various spectral extraction regions to form a picture of the cavity wall and characterize the interaction between this supernova and the local interstellar medium. We find that a series of regions along the edge of the X-ray emission appears to trace out the location of the cavity wall. The best fit plasma models result in two temperature component equilibrium models for each region. The low temperature components have densities that are an order of magnitude higher than the high temperature components. The high density plasma may exist in the cavity wall where it equilibrates rapidly and cools efficiently. The low density plasma is interior to the enhancement and heated further by a reverse shock from the wall. Calculations of shock velocities and timescales since shock heating are consistent with this interpretation. Furthermore, we find a bright knot of emission indicative of a discrete interaction of the blast wave with a high density cloud in the cavity wall with a size scale ~0.1 pc. Aside from this, other extractions made interior to the X-ray edge are confused by line of sight projection of various components. Some of these regions show evidence of detecting the cavity wall but their location makes the interpretation difficult. In general, the softer plasmas are well fit at temperatures kT~0.11 keV, with harder plasmas at temperatures of kT~0.27 keV. All regions display consistent metal depletions most notably in N, O, and Ne at an average of 0.54, 0.55, and 0.36 times solar.

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Blobrana


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Veil Nebula
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The Veil Nebula is part of the Cygnus Loop which comprises several NGC objects. Shown here is NGC 6992 in the Eastern Veil. The Veil Nebula is a faint supernova remnant that exploded some 5000 years ago, and since then it has been expanding on the sky to cover some 3 degrees. Its fine and intrincated filaments are attributed to a thin shock wave propagating into space and seen edge-on.
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Blobrana


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RE: Cygnus Loop
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Title: The Ejecta Distributions of the Heavy Elements in the Cygnus Loop
Authors: Hiroyuki Uchida, Hiroshi Tsunemi, Satoru Katsuda, Masashi Kimura, Hiroko Kosugi

We analysed the metal distribution of the Cygnus Loop using 14 and 7 pointings observation data obtained by the Suzaku and the XMM-Newton observatories. The spectral analysis shows that all the spectra are well fitted by the two-kT_e non-equilibrium ionisation plasma model as shown by the earlier observations. From the best-fit parameters of the high-kT_e component, we calculated the emission measures about various elements and showed the metal distribution of the ejecta component. We found that the distributions of Si and Fe are cantered at the southwest of the geometric center toward the blow-out region. From the best-fit parameters, we also estimated the progenitor mass of the Cygnus Loop from our field of view and the metal rich region with a radius of 25 arcmin from the metal center. The result from the metal circle is similar to that from our entire FOV, which suggests the mixing of the metal. From the results, we estimated the mass of the progenitor star at 12-15\MO.

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Title: The Abundance Inhomogeneity in the Northern Rim of the Cygnus Loop
Authors: Hiroyuki Uchida, Hiroshi Tsunemi, Satoru Katsuda, Masashi Kimura, Hiroko Kosugi, Hiroaki Takahashi

We observed the northern rim of the Cygnus Loop with the Suzaku observatory in 5 pointings (P21-P25). From the spatially resolved analysis, all the spectra are well fitted by the single component of the non-equilibrium ionisation plasma model. From the best-fit parameters, we found that the abundances of the heavy elements are significantly lower than the solar values except those at the outermost edge in P21 and P22. The origin of the depleted metal abundances is still unclear while such deficiencies have been reported from many other rim observations of the Loop. To explain these depletion at the rim regions, we considered the several possibilities. The effects of the resonance-line-scattering and the grain condensation lower the values of the abundances. However, these are not sufficient to account for the abundance depletion observed.
We found that the abundances at the outermost edge in P21 and P22 are higher than those at the other regions. From the morphological point of view, it is reasonable to consider that this abundance inhomogeneity is derived from the breakout or the thinness of the cavity wall of the Loop.

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The veil nebula
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Uncovering the Veil Nebula - exploding stars
 
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