The Latin word cumŭlus arrived in Castilian as cumulus. The concept can be used to name the accumulation or the messy crowding of various elements.
For example: “When the meeting ended, I experienced a host of sensations”, “My life is a heap of problems, I need a vacation”, “The accumulation of government errors caused this social crisis”.
In this framework, if someone refers to the “Accumulation of difficulties” that he had to go through to reach a goal, he will be referring to all the problems he had to overcome to meet his objective.
In the field of astronomy, on the other hand, the cumulus is called set of little stars which is thick to the eye. Star clusters are generated by the attraction produced by the mutual gravity of the stars.
According to the traditional classification, it is possible to distinguish open star clusters from globular ones. The open clusters are made up of young stars (whose antiquity may be between one hundred and one billion years), while globular clusters they are made up of old stars, which can be over a billion years old.
Open clusters, on the other hand, present a lower amount of stars than globular clusters. They also disintegrate over time due to their interaction with molecular clouds as they move through the galaxy, while globular ones have higher degrees of stability and density, which makes them less prone to disintegration, although this does not prevent them from sooner or later they are destroyed.
Beyond the differences in the number of stars (which inevitably affects the mass of both types of clusters) and the age of each one, it is also possible to distinguish them by their richness in metals that they present (the open ones surpass the globulars in this aspect) and by their orbit (the globulars belong to the population of the halo, and the open ones, to that of the disk).
Despite all that has been said, the dimensions of their nuclei are not very different: both in open and globular clusters, it can be measured in a few parsecs (the unit called parsec or parsec is used in the field of astronomy and its definition is the distance at which a Unit astronomical joins with an arc angle one second).
In the 1980s and 1990s, some researchers discovered that this classification was not sufficient to include all types of star clusters that exist. In the Magellanic Clouds, to cite an example, there are clusters of dimensions comparable to those of globulars, although of an age that does not allow them to be located in this group. Outside of our galaxy Stellar clusters with similar characteristics have also been discovered, with masses much higher than globular ones, and are called superclusters.
In the Milky Way there are also superclusters, and some of them lie behind huge clouds of dust. It is important to distinguish star clusters from stellar associations, groups that are not united by gravity and that present a slow dispersion.
In the field of meteorology, the clusters are cloud clusters characteristics of the summer season, which resemble mountains with snow. Also calls cumulus, these clouds have an outstanding development in the vertical direction and their edges are bright and well defined.
For the geology, cluster is the crystal gathering in magma. The notion is also used to refer to the rock that results from this accumulation process.
The cytologyFinally, it appeals to the idea of cluster of differentiation to refer to the antigens found on the surface of leukocytes, used to identify the class of cell and its activity.
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