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Difflimited
member
Reged: 01/10/06
Posts: 30
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Hi all- my backyard suburban skies are extremely light-polluted,especially the southern horizon area--i am lucky when I can see the teapot asterism naked eye. For the heck of it I observed M22. As expected it was generally washed out. But amazingly, probably 2 dozen individual stars shone brightly over the general haze of M22. My thought is that these are supergiants in M22 that become visually prominent when the general glow of fainter stars of M22 recede into the background haze. Ordinarily M22 is so bright and "resolves" so well that individual stars get lost in the general blaze of the globular. Under dark sky sites at twilight, I remember getting the same visual impression of some globulars. Anyway, it goes to show observing from any site can be interesting and worthwhile...there are always new things to experience.
keep looking up,
peter
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David Knisely
Postmaster
Reged: 04/19/04
Posts: 6785
Loc: Beatrice, Nebraska
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Quote:
Hi all- my backyard suburban skies are extremely light-polluted,especially the southern horizon area--i am lucky when I can see the teapot asterism naked eye. For the heck of it I observed M22. As expected it was generally washed out. But amazingly, probably 2 dozen individual stars shone brightly over the general haze of M22. My thought is that these are supergiants in M22 that become visually prominent when the general glow of fainter stars of M22 recede into the background haze. Ordinarily M22 is so bright and "resolves" so well that individual stars get lost in the general blaze of the globular. Under dark sky sites at twilight, I remember getting the same visual impression of some globulars. Anyway, it goes to show observing from any site can be interesting and worthwhile...there are always new things to experience.
keep looking up,
peter
Well, from a dark sky site with a really big scope, M22 is beyond words. With a 25 inch Obsession at the Nebraska Star Party, we could see *color* in the brighter stars and one reddish star in particular stood out almost right in the middle of the cluster. It was a sight I won't soon forget. Clear skies to you.
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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info
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palsing
member
Reged: 08/11/05
Posts: 95
Loc: Poway, CA
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Quote:
...I observed M22... probably 2 dozen individual stars shone brightly over the general haze of M22.
Every year at CalStar (next month!) Kent Wallace shows M-22 to anyone who wants to look these red supergiants. Kent has the ability to point his 20" to M-22 while it is still quite light, the sky is still discernably blue, and only a few bright stars can be seen. Under these circumstances, you are so right, it is quite a treat to behold.
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Paul
25" Obsession
5.5" Newt - finder (Cometcatcher)
Hutech 22 X 100 binos w/LPS-P2 filters
Canon 10 X 30 IS binos
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GlennLeDrew
professor emeritus
Reged: 06/18/08
Posts: 630
Loc: Ottawa, Ontario, Canada
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To be technically correct, they're red giants, not supergiants. And indeed, in any globular the brightest members will be giants, except for the odd blue straggler (thought to be the more-massive and hence hotter offspring from the merger of the components of a close binary.)
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Mediocre minds discuss people. Good minds discuss events. Great minds discuss ideas.
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Tony Flanders
Carpal Tunnel
Reged: 05/18/06
Posts: 2103
Loc: Cambridge, MA, USA
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Quote:
To be technically correct, they're red giants, not supergiants. And indeed, in any globular the brightest members will be giants, except for the odd blue straggler ...
Glen LeDrew took the words right out of my mouth.
To expand on this a little, supergiants are, by their nature, all very young, with lifetimes measured in millions of years. Being hot and massive, they burn out and turn into white dwarfs or neutron stars quite rapidly.
All the globular clusters in the Milky Way are very old -- nearly as old as the galaxy itself. So any star in a globular cluster that's significantly more massive than the Sun has already burned out by now. The reason that globular clusters are harder to resolve than most open clusters is partly their distance but also the lack of any genuinely bright stars.
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Tony Flanders
eyeglasses
6x15 and 8x32 monoculars
8x25, 7x35, 10x30 IS, 10x50, and 15x70 binoculars
70mm and 100mm achromatic refractors
4.5", 7", and 12.5" Dobs
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