Astronomy

Astronomy is the science that studies matter and energy contained in the Universe, considering its distribution, movement, constitution and composition, evolution. More in general, we can say that astronomy studies all the Universe intended as the space-time continuum permeated by matter and radiant energy in which it is immersed. Astronomy is particularly concerned with the Solar System and its components (Sun, planets, comets, meteors, etc.).

Etymologically, the word “astronomy” comes from the Latin astronomĭa, which in turn comes from the Greek ἀστρονομία (‘astronomy’ consisting of ἄστρον ‘astron’ “star” and νόμος ‘nomos’ “law, norm”). Most sciences use the Greek suffix λογία (‘logia’ “treatise, study”), such as cosmology and biology. In fact, “astronomy” could have taken the name of astrology, but this designation was given to what is considered a pseudoscience, but in the beliefs of many peoples was intended to predict the future through the study of the sky. Although both share a common origin, they are very different: while astronomy is a science that applies the scientific method, modern astrology is a pseudoscience that follows an unsubstantiated belief system.

On a larger scale, astronomy studies fixed stars, star clusters, interstellar matter throughout the Universe, and galaxies. According to the subject of study and according to the research methods and instruments used, astronomy is divided into several branches. The first major division is between classical astronomy and astrophysics. Classical astronomy owes this definition to the fact that until the middle of the nineteenth century it brought together all the methods of investigation and theorizing carried out in the field of astronomy; today for classical astronomy is meant the set of astrometry and celestial mechanics.

The purpose of astrometry or position astronomy is to determine the positions of celestial bodies on the sphere of the sky, to fix on the sphere itself reference systems (celestial coordinate systems), to establish methods for determining the flow of time and geographical coordinates. In addition, position astronomy is interested in the motion of the stars with respect to the celestial sphere, taking into consideration, however, only the kinematic character. The dynamic character of this motion constitutes the field of investigation of celestial mechanics.

The mathematical and geometrical instrument at the basis of astrometry and celestial mechanics is spherical astronomy, a set of notions, dating back over the centuries, of mathematical and geometrical character, which make possible the interpretation of the observed phenomena.

Starting from the second half of the nineteenth century, the progress of knowledge of physics, chemistry and the same classical astronomy favored the development of another important sector of astronomy, astrophysics, which, using specialized techniques, studies the nature of celestial objects and tries to establish a parallel with phenomena verified in the laboratory.

The union between classical astronomy and astrophysics is realized, in a restricted sense, by a particular branch, the stellar statistics, that, to study the disposition and the movements of the stars of the Galaxy, uses methods and instruments of both sciences; the results of the stellar statistics have been overcome with the advent of the most powerful means of radio astronomy.

Other important branches are cosmogony and cosmology that deal with problems formally similar, but on a considerably different scale (1013 times): cosmogony is interested, at the level of the solar system, the formation and evolution of concentrations of matter, while cosmology considers the whole Universe.

Astronomy is not an isolated science: both for the practical aspect (execution of observations, improvement and construction of suitable instruments), and for the theoretical one (deduction of laws and derivation of results from observations; calculations; prediction of astronomical phenomena) is often required a wealth of knowledge that refers to the bases of physics, nuclear physics, mathematics, chemistry; on the other hand, astronomy has often allowed, indeed produced, considerable progress in sciences and techniques related to it.

The technological progress of observation instruments, the systematic use of artificial satellites and space probes have allowed the collection of an enormous amount of information: new objects have been discovered, unexpected properties of already known objects have been brought to light, and new branches of science have been born, as for example that of lunar geology and in a broader sense of planetology, which follows the direct knowledge of planets, satellites, comets and asteroids, achieved with the study of these bodies in situ carried out with probes of various kinds.

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