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NGC 6397 (also known as Caldwell 86) is a globular cluster in the constellation Ara that was discovered by French astronomer Nicolas-Louis de Lacaille in 1752. [9] It is located about 7,800 light-years from Earth, [3] making it one of the two nearest globular clusters to Earth (the other one being Messier 4).
A supervised classification is a system of classification in which the user builds a series of randomly generated training datasets or spectral signatures representing different land-use and land-cover (LULC) classes and applies these datasets in machine learning models to predict and spatially classify LULC patterns and evaluate classification accuracies.
A stellar association is a very loose star cluster, looser than an open cluster. A moving group is the remnant of such a stellar association. [1] Members of stellar associations and moving groups share similar kinematic properties, as well as similar ages and chemical composition. The list (below) is sorted by the distance to the Solar System.
Unsupervised classification (also known as clustering) is a method of partitioning remote sensor image data in multispectral feature space and extracting land-cover information. Unsupervised classification require less input information from the analyst compared to supervised classification because clustering does not require training data.
The term "The Local Group" was introduced by Edwin Hubble in Chapter VI of his 1936 book The Realm of the Nebulae. [11] There, he described it as "a typical small group of nebulae which is isolated in the general field" and delineated, by decreasing luminosity, its members to be M31, Milky Way, M33, Large Magellanic Cloud, Small Magellanic Cloud, M32, NGC 205, NGC 6822, NGC 185, IC 1613 and ...
Globular cluster: Nearest globular cluster to the Earth. Also the first globular cluster known to have exoplanets (PSR B1620-26b) Messier 12: 74.4 [28] Messier 70: 68 [29] NGC 290: 66 [30] Open cluster: Messier 28: 60 [31] Globular cluster: Messier 18: 52.4 [32] Open cluster: The following notable star clusters are listed for the purpose of ...
The BCG of this cluster was also the most distant galaxy of the time. [51] [53] Gemini Cluster 1932 − 1936 0.075 23 000 The BCG of this cluster was the most distant galaxy at the time. [53] [54] WH Christie's Leo Cluster 1931–1932 19 700 The BCG of this cluster was the most distant galaxy known at the time. [51] [54] [55] [56] [57]
Below there are lists the nearest stars separated by spectral type. The scope of the list is still restricted to the main sequence spectral types: M, K, F, G, A, B and O. It may be later expanded to other types, such as S, D or C. The Alpha Centauri star system is the closest star system to the Sun.