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| « back to overview Nebula | Load higher resolution (1800 x 1100 Pixel 3500 x 2100 Pixel) | Object description |
Our image shows a slightly misaligned mosaic (the northwestern segment with "Pickering's Triangle" is missing) of the Veil Nebula (Cygnus Loop). It is an extended, almost circular supernova remnant (SNR) in the constellation of Swan and is the part of the Cygnus Loop visible in the optical spectrum, a collection of emission nebulae. It consists mainly of the individual nebulae NGC 6992 (eastern part, on the left in the image), NGC 6960 (western part, on the right in the image) and NGC 6979 (centre). The Cirrus Nebula is the perfect example of a supernova remnant and has an apparent diameter of 3 degrees in the sky. NGC 6960 has the popular German name "Sturmvogelnebel" and in English it is called " Witch's Broom".
The Veil Nebula was formed by a supernova explosion about 5000 to 15000 years ago. The distance to the solar system is not known exactly, the information varies - depending on the measuring methods - between 1500 and 4500 light years. However, new studies by NASA and ESA suggest a distance of around 2400 light years (Robert A. Fesen, et.al, 2018) and an age of about 8000 years. The compact remnant (neutron star, pulsar or black hole) of the supernova has not yet been found. Assuming a distance of 2400, the true diameter of the nebula is about 130 light years.
The gas ejected by the supernova explosion expands and spreads out almost spherically at around 180 kilometres per second. In the process, it collides with the surrounding interstellar medium and forms a structure of luminous filaments and nebulae.
The two large nebular segments NGC 6960 and NGC 6992 show most clearly that the supernova remnant is expanding and colliding with the interstellar medium in the process. In the west (NGC 6960, right in the mosaic), the "collision barrier" consists of a dark molecular cloud. Fine filaments form at the fronts, which are ionised by the collision energy and radiate light. Depending on the chemical elements present in the nebular filaments, the filaments glow red (H-alpha, nitrogen and/or sulphur) or blue (hydrogen H-beta) to blue-green (O-III). Compared to the other regions in the Cirrus Nebula, the O-III fraction is highest in NGC 6960. This is shown by the striking turquoise colouring, so the Cirrus Nebula glows by itself.
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The
prominent bright star near NGC 6960 - 52 Cygni -
has nothing to do with the Cirrus Nebula, because it is far in the foreground
at a distance of about 200 light-years. It is assigned to the spectral type G
9.5-III. The brightest parts of the nebula were discovered by Friedrich Wilhelm Herschel in 1784. The southernmost part of NGC 6992 is catalogued as NGC 6995 and was discovered in 1825 by John Herschel, Herschel's son, using his father's telescope. The fainter parts of the nebula were discovered later - in 1866 and 1873 - by the American astronomer Truman Henry Safford (IC 1340) and by Lawrence Parsons, the 4th Earl of Rosse (NGC 6974). « Click here or the thumbnail to load a large annoted image and a size comparison to the full moon. |
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« The
composite image shows data composed of ROSAT X-ray (blue), GALEX UV (white) and
WISE 12- of 22?m infrared radiation (blue and red), and impressively shows the
entire, almost circular "bubble" of the supernova remnant. Also clearly
standing out in the west is the brownish molecular cloud colliding with the
filaments of NGC 6960 at a high speed of 180 kilometres/second. To the north
lies a region nearly free of interstellar clouds.Click
here or the thumbnail to load a large image. Credit: https://arxiv.org/pdf/1809.01713.pdf aus:" THE CYGNUS LOOP'S DISTANCE, PROPERTIES, & ENVIRONMENT DRIVEN MORPHOLOGY" Due to the high popularity of the Cirrus Nebula, there are a large number of interesting websites on the internet. We have linked some of them here for you. High-resolution detail photographs of the NASA/ESA can be seen here. Detailed info, maps and descriptions can also be found here and here. |
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