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M13 is 22,200 to 25,000 light-years away from Earth, [9] and the globular cluster is one of over one hundred that orbit the center of the Milky Way. [ 17 ] [ 18 ] The stars in this cluster are firmly in the Population II category, markedly lower in metals than Population I stars like the Sun and most other stars in the Sun's close proximity.
The Arecibo message is an interstellar radio message carrying basic information about humanity and Earth that was sent to the globular cluster Messier 13 in 1974. It was meant as a demonstration of human technological achievement, rather than a real attempt to enter into a conversation with extraterrestrials. [1] [2]
The first known globular cluster, now called M 22, was discovered in 1665 by Abraham Ihle, a German amateur astronomer. [4] [5] [6] The cluster Omega Centauri, easily visible in the southern sky with the naked eye, was known to ancient astronomers like Ptolemy as a star, but was reclassified as a nebula by Edmond Halley in 1677, [7] then finally as a globular cluster in the early 19th century ...
The Messier catalogue comprises nearly all of the most spectacular examples of the five types of deep-sky object – diffuse nebulae, planetary nebulae, open clusters, globular clusters, and galaxies – visible from European latitudes. Furthermore, almost all of the Messier objects are among the closest to Earth in their respective classes ...
Globular cluster masses can be determined by observing the proper motion of nearby stars influenced by the cluster [1] [2] or by estimating the cluster's relaxation time. [ 3 ] Open clusters
These are globular clusters within the halo of the Milky Way galaxy. The diameter is in minutes of arc as seen from Earth. For reference, the J2000 epoch celestial coordinates of the Galactic Center are right ascension 17 h 45 m 40.04 s, declination −29° 00′ 28.1″.
The following are lists of clusters: List of galaxy groups and clusters; List of open clusters; List of globular clusters; See also. List of superclusters
Advanced Placement (AP) Human Geography (also known as AP Human Geo, AP Geography, APHG, AP HuGe, APHug, AP Human, HuGS, AP HuGo, or HGAP) is an Advanced Placement social studies course in human geography for high school, usually freshmen students in the US, culminating in an exam administered by the College Board. [1]