The Great Globular Cluster in Hercules (M13, NGC 6205)

All Images Copyright Steve Cannistra

Please click here or on image for a higher resolution view.

Magnitude:  7.0
Size:  0.36 degrees
Distance: 25,000 light years
RA: 16h 41m 38s
Dec: 36 degrees 28' 03"

No one forgets their first view of M13 in the eyepiece.  It's a remarkable site, with speckled stars arising from the center giving it an almost 3-dimensional appearance.  The above photograph represents an approximately 1 degree FOV, which is enough to appreciate M13 in the context of its neighbors like the galaxy NGC 6207 in the upper right.  This globular cluster is 25,000 light years away, orbiting near the center of our galaxy.  Globular clusters contain stars at such high density that the night sky would be filled with light, and planetary orbits would be unstable due to gravitational influences from nearby stars.  Also, the stars of M13 are very old and consequently contain very little metal (they were formed at a time when basic elements like iron had not yet been forged by other stars).  So it is unlikely that earthlike planets formed around any of the stars in this cluster.  The message sent to M13 by the Arecibo Radio Telescope team in 1974 will most likely fall on deaf ears.

Photographic Details:
Date:  September 2, 2004
Takahashi Sky 90 at f4.5 with field flattener/focal reducer, on the G11 Losmandy Mount.
Autoguider:  SBIG STV with e-finder.
Camera:  SXV-H9
Astronomik RGB type II filter set.
Exposures:  RGB composite.  10 x 2' for R, G, and B each, binned 1 x 1, 60 minutes total.
Conditions:  Temperature 55 degrees F; average transparency; average seeing; calm.
No darks or flats used.  Two-star aligned in ImagesPlus; Sigma combined using RC Sigma Reject in MaximDL, followed by color combine and DDP in ImagesPlus.  Correction of gradients in each channel using the background compensation tool in ImagesPlus.  Subsequent levels and curves adjustments in Photoshop CS (16 bit format).

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