| JayinUT |
| (I'm not Sleepy) |
| 07/03/09 11:13 AM |
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Re: NGC 6441
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Nice report. I fear that by the time the weather clears up where I live (next Tuesday or so) the moon will be full than wanning gibbious and by the time it gets back past last quarter the clouds will return.
Thanks for posting on NGC 6441. I did some research and found that the planetary is located near the globular's core/center so I would say that most average scopes won't have a chance to pull that out (maybe a very large dob but others can comment/correct me). My information for that came from here.
In case you don't want to click the link here is the info:
Quote:
JaFu 2 (diameter of 5" = 0.22 pc) in NGC 6441 is very likely a cluster member, having similar velocity (37 km/s), and extinction (E_B-V=0.4), in addition to being close to the cluster center (37").
I also found this site where they discuss that a 20" or higher aperture scope is needed with an OIII filter and a very dark site (they list it as perhaps an ultimate, well perhaps one of the ultimate, greatest planetary challenges).
I also found this article on NGC 6441 where the authors discuss the difficulties in labeling NGC 6441 as to what type of globular it is based on the fact
Quote:
that the classification of NGC 6441 into one or the other of the usual Oosterhoff groups is difficult. The long periods of the RRab stars and the relatively large proportion of c-type pulsators are more typical of Oosterhoff II than Oosterhoff I systems, although we again note that 〈Pab〉 is unusually large even for Oosterhoff II. In contrast, the mean luminosity of the NGC 6441 RRc stars, as found by applying the Simon & Clement (1993a, 1993b) method (see § 5.1), is consistent with values found in Oosterhoff I clusters such as M3.
Furthermore in their conclusion the authors state
Quote:
NGC 6441 stands out as one of the more unique globular clusters of our Galaxy. NGC 6441 is confirmed to be a metal-rich globular cluster exhibiting an unusual HB morphology. (and) NGC 6441 was shown to stand apart from other Galactic globular clusters in that it does not fit in the Oosterhoff classification scheme. The mean periods of the RRab stars in the cluster are as long as or even longer than the typical, more metal-poor, Oosterhoff type II clusters. This contradiction in the trend of increasing period with decreasing metallicity for a given amplitude implies that the metallicity-luminosity relationship for RRLs is not universal—if, in fact, the RRLs in NGC 6441 do share the cluster's relatively high overall metallicity.
So, again, I have to thanks for bringing up this globular and allowing me the opportunity to increase my own understanding of the many wonders that this object holds. That is one thing I love about this hobby, the opportunity to learn something everytime I research an object I or someone else has observed and to find out some interesting facts about the object from the scientific community.
Here is a link to the second article incase someone wants it in PDF instead of the HTML I used: HTML or PDF Article
Edit: If your looking for planetary nebula's to view here is a list of summer objects: Planetary Nebula Obervers Guide BTW you can click on the home on the top (horrible midi music) and then go to the left and find seasonal PN's and get more by season or download his database.