I've tried another bout of processing my M22 images, using a method to set color balance that relies on the background tones of the exposures. The result looks a little less crisp, and the colors are peculiar. But here it is, in case it has any interest: http://www.slas.us/gallery2/main.php?g2_itemId=2036 Jay, I very much appreciate all the great info you've provided! I may write another globular cluster piece later one, when people have forgotten I've board everyone on the topic, and then I could use some of the material you dug up. Hope you and your wife have a great tirp and a fine anniversary. -- Best wishes, Joe --- On Sun, 6/14/09, Jay Eads <jayleads@gmail.com> wrote: From: Jay Eads <jayleads@gmail.com> Subject: Re: [Utah-astronomy] M22's Blue Stars (continued) To: "Utah-Astronomy" <utah-astronomy@mailman.xmission.com> Date: Sunday, June 14, 2009, 10:24 PM Another article at http://www.eurekalert.org/pub_releases/2009-04/sfsu-lco042209.php tells us that 18 white dwarfs were found in NGC 6397.  White dwarfs are very common in a globular cluster but what is interesting about these 18 is that instead of being made of carbon and oxygen they are made of Helium.  These were captured by the Hubble in new images and they are "the first extensive sequence of helium-core white dwarfs to be observed in a globular cluster."  The article implies that these stars were cut off at the helium stage because they are part of a binary system with a heavy star companion because they are found in the central regions and not all around the cluster. One of the astronomers is Professor Adrienne Cool at SF State University and she says: "Cool suggests that a star that goes on to become a helium-core white dwarf must have a close companion so that when the star became a red giant and expanded, its outer layers spilled onto the companion. The star never had the chance to reach maturity and burn its helium into carbon and oxygen" (see, it is Cool to be involved with Astronomy; just ask the professor; sorry couldn't resist). The actual publication by the astronomers will come out on July 1st, 2009 in Astrophysical Journal. On a side note NGC 6397 was the globular used in a 2004 study where berylium content of two stars were measured and allowed the astronomers in the study to deduce the time that elapsed between the rise of the first generation of stars in the galaxy and the first generation of clusters. This information was used then to arrive at an age of the Milky Way Galaxy at around 13.6 billion years old.  You can see a recap of that at http://www.eso.org/public/outreach/press-rel/pr-2004/pr-20-04.html In 2006 another Hubble survey  found the faintest stars in this cluster by examining red dwarfs and white dwarfs and comparing them. Of interest in the article (which I don't think we can photograph with earth bound telescopes) is this statement: "Hubble showed that the dimmest white dwarfs have such low temperatures that they are undergoing a chemical change in their atmospheres that makes them appear bluer rather than redder as they cool. This phenomenon had been predicted, but never observed."  This article is found at http://hubblesite.org/newscenter/archive/releases/2006/37/full/ So another item to add to the list of Globular Clusters is that the stars in the Globular are used by professional astronomers to determine the age of the universe and in this case, the Milky Way Galaxy, which is near the age of the universe itself. Joe, if you read this, thank you for providing me with something to do on these very cloudy and rainy nights. I've learned so much about Globular Clusters (more than I have shared fearing I am boring others) and the current research into them is interesting and intriguing. When I get a good night (soon I hope, before I go to San Diego for five days with my wife for our anniversary in a week) and I take my time to look at the wonderful globulars that are rising around 11:00p.m. to 1:00a.m. to the south south-western sky, I will have a far greater appreciation of not only these objects, but what we are learning from them. For enriching my knowledge I express my gratitude yet again to you. Jay _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com