M 13

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Date
2015/06/18

Observation place
 Spain

Technical

TelescopePlanewave 431mm - 17 ″, 2mm FL, f / 939
MountParamount ME
Imaging cameraSBIG STL-11000M - regulated at -20o Celsius
Image typeL (RGB) (Vs for synghetic green)
ExhibitionLuminance (10 x 6,67 'bin 2 × 2), R and B (4 x 5' bin 3 × 3 each)
PretreatmentMaxim DL
TreatmentPhotoshop and PixInsight
Specific treatmentCreate a synthetic green image

Object description

Object typeGlobular cluster "The Great Cluster of Hercules"
ConstellationHercules
Visual magnitude5,9
Distance23000 light years
Diameter150 light years
Dimension seen from Earth20 arc minutes
The globular cluster M13, very often called the Large Cluster of Hercules, is among the most imposing objects of the Messier catalog. It is considered to be the most beautiful globular cluster in the boreal sky. It was discovered by Edmond Halley in 1714, and added by Charles Messier in his catalog on June 1, 1764.

Containing more than 100 stars, it is also one of the oldest objects: its age is estimated at 000 or 12 billion years, that is to say immediately after the creation of the universe which is 13 billion years old! It appears with a diameter of 13,73 arc minutes, or an actual diameter of 20 light years. However, it has the particularity of containing many young stars (membership confirmed by their angular speed), which is unusual for a cluster of this age: scientists believe that these stars were not born inside the clusters, but were instead captured by the latter.  

Messier 13 was used in 1974 (November 16) as a target for sending a message to a potential extraterrestrial civilization. This message was sent from the Arecibo radio telescope, which is also participating in the SETI project. It contained information such as numbers, the atomic number of hydrogen, carbon, nitrogen, oxygen and phosphorus, DNA data, the shape and size of a human, the Earth's population, and Earth's position in the solar system. It will take more than 25000 years to achieve this (as much for the eventual answer)…  

M13 can be seen with the naked eye under a sky without light pollution. We then see it in the form of a white spot. With a telescope or a telescope with a diameter of 150mm and more, we can solve some details of the cluster.

In my image, we also see on the left the small galaxy IC4617 presented in the following annotation (made with the PixInsight software using my image):
https://ciel-astro-ccd.com/m13_annota.jpg

It appears small because it is very far from the earth, about 490 million light years. It still contains billions of stars. Seen from our earth, it has a visual magnitude of only 16. This very low light explains that in several photos, we cannot distinguish this galaxy very close to M13 visually. Its dimension seen from the earth is only 1,20 x 0,40 arc minutes (the Moon has a diameter of about 30 'of arc). Here is a very interesting article on this galaxy: http://www.astrosurf.com/stog/archives/ic4617/i4617.htm
Richard Beauregard
Sky Astro - CCD
My impression "We cannot be alone in this gigantic universe"