Re: [APML] OT: A Deep M13

["Stuart Heggie" <Stuart.J.Heggie@sympatico.ca>]

Amazing! The colour is beyond vibrant - really nice one!

Stuart
----- Original Message ----- 
From: "Robert Gendler" <robgendler@worldnet.att.net>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Saturday, April 23, 2005 11:10 AM
Subject: [APML] OT: A Deep M13


> Hi all,
> Here's an M13 collaboration, data by Jim Misti, processed by me.
>
> http://www.robgendlerastropics.com/M13JM.html
>
> Just a little clarification about the presence of blue stars in many
> globulars. Many of us have erroneously attributed the blue population
> stars to "Blue Stragglers" which have received lots of publicity recently.
> Probably the vast majority of blue stars in globulars are blue horizontal
> branch stars which having exhausted their hydrogen fuel are now
> fusing helium to carbon. The other bland colored or white stars are mostly
> RR Lyrae stars which surprisingly make up a substantial population of many
> globulars. The blue stragglers which are likely the result of either
> collisions
> in high density central regions or mass transfer in binary systems are
> considerably
> dimmer than the helium burning horizontal branch stars and are mostly
> located
> in the central dense core of globulars.
>
> In summary many of the blue stars we see in CCD images of
> globulars are blue horizontal branch helium burning stars and not
> blue stragglers which are mostly central and less luminoius than the
> other populations mentioned.
>
> I hope that professional astronomers out there will let me know if I got
> some of this wrong.
>
>
> Rob Gendler
> email: robgendler@att.net
> Web Site: http://www.robgendlerastropics.com
>
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