About 145
light-years in
diameter, M13 is composed of several hundred thousand
stars, with estimates varying from around 300,000 to over half a million. The brightest star in the cluster is a
red giant, the
variable star V11, also known as V1554 Herculis, with an apparent visual magnitude of 11.95. M13 is 22,200–25,000 light-years away from
Earth, and the globular cluster is one of over one hundred that orbit the center of the Milky Way.Single stars in this globular cluster were first resolved in 1779. Compared to the stars in the neighborhood of the
Sun, the stars of the M13 population are more than a hundred times more densely packed. They are so close together that they sometimes collide and produce new stars. The newly formed, young stars, known as "
blue stragglers", are particularly interesting to astronomers.The last two variables (V63 and V64) were discovered from Spain in April 2021 and March 2022 respectively.
The 1974
Arecibo message, which contained encoded information about the human race, DNA, atomic numbers, Earth's position and other information, was beamed from the
Arecibo Observatory radio telescope towards Messier 13 as an experiment in contacting potential extraterrestrial civilizations in the cluster. M13 was chosen because it was a large, relatively close star cluster that was available at the time and place of the ceremony. The cluster will move through space during the transit time; opinions differ as to whether or not the cluster will be in a position to receive the message by the time that it arrives.
Source: Wikipedia
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