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Image Details: NGC 0559

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NGC 0559

Object/Name: NGC 0559 (Caldwell 8, The Ghost's Goblet) Image Details:
Type: Open Cluster and Supernova remnant Hydrogen Alpha:10.00 min. (29) – 290.00 min. 1x1
Constellation: Cassiopeia Red:5.00 min. (7) – 35.00 min. 1x1
RA: 01 hours 29.5 minutes Green:5.00 min. (7) – 35.00 min. 1x1
Dec: +63 degreees 18 minutes Blue:5.00 min. (8) – 40.00 min. 1x1
Distance: 3,700.0 light years Total Time:400 minutes
Magnitude: 9.5 mag   
Size: 7.0 x 7.0 arc minutes   
Imaging Dates: 1 - 2 September 2007   
Location: Dark Horse Observatory, Kimberton, PA 19460 U.S.A.   
Telescope: Takahashi BRC-250 Mount: Mountain Instruments MI-250
CCD: SBIG ST-10XME Rotator: Optec Pxyis Rotator
Focuser: Finger Lakes Instruments DF2 Filters: Astrodon Series E
Software Used:
  CCDStack MiraPro Professional
Photoshop CS2 Russel Croman’s Gradient Xterminator
Noel Carboni’s Astronomy Tools  
Detailed Information:
As some of you know, other than a six month period back in the 1980s, I have only been active in astronomy for a little over two years. I was never much of a mathematician and only just eeked out an A minus in college calculus. I took Physics for Poets to avoid the mathematical portion of that subject. Astronomy and Cosmology are pretty mathematical and pretty dense subjects so I have a strong feeling of insecurity in these areas. Add this to my recent introduction to this hobby and you can understand why I feel that I don’t know much about astronomy. Because of this I have been trying to read about some of the areas. I recently became inspired to learn more about star clusters after imaging M13. I was reading a newly acquired book, Star Clusters and How to Observe Them by Mark Allison (which I would recommend to anyone interested in starting to learn about this subject) when I came across some interesting information. On page 19 while discussing the death of star clusters Allison mentions that star death can occur by a member going supernova. He stated that in the constellation Cassiopeia there is a cluster, NGC 559, which “is the host of a supernova remnant, the gaseous filaments shedded by a supernova explosion.” He also comments that since open clusters are generally quite young, “it is quite unusual to find supernova remnants within open clusters.” For reasons that I cannot specifically explain, this intrigued me. I determined that this would be a good target for imaging if I could find out more about it. I decided that it was time for some internet research. After searching for quite a while the only images of this region that I was able to retrieve were pretty uninspiring black and white images taken in sky surveys. There were a couple of poor shots by amateurs, but no careful images were uncovered in my searches. I discussed this with Frank and he later confirmed the same result with his search. Moreover, none of these images provided anything that suggested a supernova remnant (SNR). It occurred to me that one reason for this might be the fact that they were all done at visible wavelengths and therefore might not have detected the H II emissions of the hydrogen left from the supernova. Another reason it might not be seen is that this could be a very faint SNR from a very old supernova and the exposures might not have been sufficiently long to capture the signal. In general for clusters, they are so much brighter that shorter exposure times and fewer frames are necessary to get excellent optical results. Again I decided to turn to my research to see if I could learn more about this SNR in NGC 559. NGC 559 is so named for its position in the New Galactic Catalog of William Herschel who first discovered it in 1787. It was also dubbed by Sir Patrick Moore as Caldwell 8 and has the more colorful appellation of “Ghost’s Goblet.” It is a rather faint cluster at only magnitude 9.5 and contains only about 120 stars. It is can be found by the frame of epsilon, delta, and gamma Cassiopeia and lies just outside of a line between epsilon and gamma Cassiopeia about 40% of the way toward the latter. Both O’Meara and Barbara Wilson comment on this open cluster as providing a nice arrangement of chains and doubles. Additionally, O’Meara says that under dark skies there is an impression of “many colored stars that glisten like jewels.” O’Meara also noted that NGC 559 is centered on a 45’-wide supernova remnant (catalogued as G127.1+0.5 R5 in David A Green’s Catalogue of Supernova Remnants). He was skeptical if the SNR was related to the open cluster based upon discrepancies in the ages of the two. I went back to the literature and found the first observation of this association was made by T. Pauls in a 1977 letter to the editor in Astronomy and Astrophysics 59, L13-L14. In this letter, Pauls refers to the radio source as G127.3+0.7 (an older name for G127.1+0.5 in the fifth revision of the Green catalogue). He commented that this overlay the open cluster NGC 559 which contained a number of yellow and red giants suggesting that the cluster was quite old. A previous estimate in 1968 by Ulf Lindoff had placed the age at around a billion years. He commented that in combination with the absence of any optical nebulosity suggested that there was little ionized gas in the cluster to generate a radio emission, the evidence suggested that the SNR had been part of the open cluster. He suggested the need for optical observations to confirm the presence of evidence of a SNR. In a later paper, T. Pauls et al. in Astronomy and Astrophysics 112, 120-123, 1982 concluded that the open cluster NGC 559 was not physically associated with G127.1+0.5 on the basis of additional radio astronomical observations that places G127.1+0.5 at a distance of about 3.8 kpc. Subsequently work by G. Joncas et al in 1989 Astronomy and Astrophysics 219, 303-307 estimated that the distance to G127.1+0.5 was between 2 and 5 kpc. This distance agreed with the previous estimate by Pauls. Since the open cluster NGC 559 was only 1.1 kpc they concluded that the two were unlikely to be associated other than by coincidence. It was not until the literature from 1993 that I could find evidence of optical examination of this area. In Astronomy and Astrophysics, 270, 393-396 (1993) K.M. Xilouris et al. describe detection of optical emission in the area of G127.1+0.5. The area of the radio emission is an almost perfectly circular region of approximately 45 arcmin in diameter. The open cluster NGC 559 is slightly displaced off center and only occupies an area of approximately 4.4 arcmin in diameter. They note that the age of the cluster is estimated to be 1.3 billion years at a distance of about 900 parsecs. Photometric observation of the area suggested that there was very little ionized hydrogen in the area. They imaged the area for a total exposure time of 105 minutes using a filter centered an 6570 Angstrom (H-alpha +[N II]) with a 75 Angstrom band pass. Using this technique they were able to image from Mount Skinakas on the island of Crete an area of diffuse nebulosity using a 30 cm Schmidt-Cassegrain f/3.2 telescope and a TI 4892 CCD detector. This gave them a field of view (32 x 48 arcmin). Unlike the filaments observed in the vicinity of nearby G126.2+1.6 the area of G127.1+0.5 has nebulosity observed in the Hydrogen alpha range. They comment that this was the first time that these faint, diffuse optical emissions have been detected. Correlation with other contour maps in IR and radio emissions as well as other calculations suggest that these areas of nebulosity are associated with G127.1+0.5 and are not connected to G126.2+1.6. This is a very complicated region of the sky and the final chapter may well have not yet been written as to the physical relationships of all these findings to each other. It was an interesting journey that left me wanting to have an aesthetic souvenir of my wanderings. I, therefore, present this image for your examination of the region in question. It is represents an H-alpha (656 nm [6560 Angstrom] with 6 nm [60 angstrom] band pass – narrower than used above) and RGB image centered on NGC 559. The beautiful star colors can be seen swimming in a swirling cloud of predominantly gray nebulosity that was captured only in the H-alpha exposures. Since these were combined as if they were luminance data they appear gray. I think that it is truly amazing that from my backyard in Kimberton, armed only with a 10 inch telescope and a commercial CCD camera I was able to capture the similar information to the 30 cm. scope on the island of Crete. I am left wondering why it took so long for this area to by visually imaged in order for this to be discovered. I am also struck by the irony that this cluster is named the Ghost’s Goblet and it overlies such a ghostly area of nebulosity! I also imaged the same region in O III and S II narrow band filters. The following image is the same area displayed in the Hubble Palette. Click on the image for the full size image.

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