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Hierarchical Structure of the Universe 56 Odessa Astronomical Publications, vol. 31 (2018) DOI: http://dx.doi.org/10.18524/1810-4215.2018.31.148048 HIERARCHICAL STRUCTURE OF THE UNIVERSE V.A. Zakhozhay V.N. Karazin Kharkiv National University, Kharkiv, Ukraine [email protected] ABSTRACT. The modern understanding of the structure нижчої ланки. За такої класифікації, підгрупи та of the Universe is discussed. The Solar System is viewed as скупчення галактик є проміжними елементами an ordinary planetary system. The neighbourhood of the крупномасштабної ієрархії об’єднань галактик. Sun is specified starting with the nearest stars and nearby Остаточний висновок: на теперішній час clusters and working outward through the Local system of встановлено повну «адресу», де находиться землянин stars, in particular, Gould’s belt. The subgroups of the у Всесвіті. Наступною незвіданою структурою світу Milky Way, our stellar system, and Andromeda are може бути лише місце нашого Всесвіту серед інших examined as components of the Local Group of galaxies. всесвітів, якщо вони існують. Special attention is paid to their astrophysical, kinematic and dynamic properties. A larger agglomeration of galaxies, 1. Hypotheses and evidence of a hierarchical called the Local Supercluster, which contains the Local structure of the Universe Group and its immediate neighbourhood is analysed. And finally, the Laniakea hypercluster to which the Local The picture of the universe formed in the early days of Supercluster and its environment belong is described along telescopic astronomy was restricted to the structure of the with its neighbours, namely the Perseus-Pisces hypercluster Solar System. At that time, there was just conjecture about and the Local Void. the stellar origin of the Milky Way and philosophic speculations about the presence of planets orbiting stars Keywords: Universe structure; hierarchy; star clusters; like those orbiting the Sun [3]. The discovery of the laws galaxy clusters; hyperclusters of motion and gravity by Isaac Newton definitely established the validity of heliocentric model of the АБСТРАКТ. Аналізуються сучасні уявлення про Universe [31]. Systematic telescopic observations initiated устрій Всесвіту по мірі віддалення від Сонця. Сонячна accumulation of data on the universe beyond the Solar система представлена як рядова планетна система. Далі System and scientific substantiation of the suggested характеризуються околи Сонця: від найближчих зір і їх hypotheses about its structure. скупчень до устрою Місцевої зоряної системи (МЗС – поясу Гулда). Аналізується гіпотеза щодо припущення, 1.1. First scientific hypotheses що за структурою і астрофізичними показниками МЗС The analysis of the accumulated telescopic схожа на маленьку галактику, яка нагадує об’єкт Ходжа astronomical observations allowed making first в спіральній галактиці NGC 6946. hypotheses about hierarchical structure of the Universe in Будова Галактики, Нашої зоряної системи, підгрупи the middle of the eighteenth century. In 1750, Thomas Андромеди аналізуються з точки зору складових Wright proposed a new concept of the Universe consisting частин Місцевої групи галактик (МГГ). Приділяється of hierarchically arranged systems with one of the увага їх астрофізичним і кінематичним властивостям. components being the disc-shaped Milky Way [44]. In За межами МГГ аналізується їх безпосереднє оточення 1755, Immanuel Kant also came to the conclusion that the та більш крупна структура – Місцеве Надскупчення Solar System formed from gaseous cosmic matter was a (МН), до якої вона належить. Далі розглядається constituent part of the Milky Way [21]. In 1771, Johann гіперскупчення Ланіакея, в якому містяться МН і його Lambert hypothesised that our Solar System was a околи. Характеризуються сусіди гіперскупчення member of one of those larger intermediate stellar systems Ланіакея: гіперскупчення Персея-Риб і Місцевий войд. which constitute the Milky Way [24]. Аналізуються прояви просторово-часового устрою Validation of the suggested hypotheses required further telescopic observations of celestial bodies. Such surveys Всесвіту та його коміркова структура. Обмірковується of the structure of the Universe were pioneered by область Всесвіту, обмежена хабблівським радіусом і її William Herschel. He found clumping of nebulae and властивості. Робиться висновок, що основними resolved the richest of them in the constellation Coma складовими серед об’єднань зоряних систем різної Berenices [11] incorporated into a rather narrow region ієрархії слід вважати групи, надскупчення та extending through the constellations Virgo, Ursa Major гіперскупчення, оскільки проглядається закономірність, and Andromeda. Since the middle of the twentieth century за якою, як правило, більш вищий рівень об’єднання this region has been identified as a part of the Local галактик включає на два порядки більше об’єктів Supercluster. In 1785, based on the results of careful Odessa Astronomical Publications, vol. 31 (2018) 57 observations and calculations of stellar parameters, independently elaborated that idea and inferred a Herschel presented the first model of the Galaxy shaped as relationship between the stars’ spectra and absolute a flattened disc in the first-order approximation [12]. magnitudes [34-36]. The plotted relationship was called Herschel’s Catalogue of One Thousand New Nebulae and the Hertzsprung-Russel diagram, and since then it is of Clusters of Stars [13] published in 1786 gave an impetus great importance for studying stellar systems. to systematic survey of star clusters. The detection of the correlation between the luminosity and period of Cepheids in the Small Magellanic Cloud by 1.2. First findings of surveys of the arrangement of Henrietta Leavitt in 1908-1912 [26, 27] contributed to the stellar systems determination of distances to the remotest stellar systems. It Increasing diameters of telescope mirrors, usage of enabled Harlow Shapley to deduce the dimensions of the clock drives to compensate for the celestial sphere Galaxy from the distribution of globular clusters on the rotation, introduction of spectral analysis and its celestial sphere relative to the Milky Way and from the implementation into observational astronomy in the presence of RR Lyrae variable stars in the relevant clusters nineteenth hundreds enabled to initiate systematic studies [38]. It turned out that all discovered star clusters and nebulae of the stellar systems, such as multiple star systems and could be split into two groups, namely those within and those star clusters, discovered by that time. Determination of the beyond the Galaxy. Further analysis of extragalactic nebulae orbital period of the double star Castor by Herschel in revealed that they consisted of stars, and that there was a 1803 resulted in the establishment of its physical duplicity correlation between their redshifts and distances (Edwin and allowed application of Kepler’s third law to its Hubble, 1929; [18-20]). Thus, a real reference framework investigation [14]. The discovery of the Doppler effect in needed for the determination of the scales of the Universe 1842 marked the start of its implementation in and its three-dimensional structure became available. astronomical observations. In particular, it enabled the The analysis of spatial arrangement of galaxies made it detection of spectroscopic binaries (Edward Pickering, possible to establish their inhomogeneous distribution in 1890; [33]). There were a total of about 10 thousand of the universe over a given range of scales. They combine double and multiple stars comprised of three to sixteen into certain structures which tend to have a common components found at that time. The complied catalogues feature – namely, that larger structures consist of those of double and multiple stars laid the foundation of their which are smaller and contain fewer galaxies. As a result, systematic investigation. galaxy groupings were classified based on different levels The discovery of the first spiral structure in the stellar of hierarchy from groups and clusters of galaxies to system Messier 51 (M51) made by William Parsons in galaxy superclusters. In the second half of the twentieth 1845 with a six-foot (72 inch) reflecting telescope, which century, it became clear that such hierarchical structures was the largest in the world back then, marked the are confined to hyperclusters which along with galaxy beginning of surveys of the structure of such stellar superclusters constitute the cellular space-time structure of systems. By the late nineteenth century, spirality was the Universe. As regards the distribution of galaxies and detected in at least 10 “stellar nebulae”; the existence of different levels of their arrangement, the concept of elliptical, lenticular and annular structures was also homogeneous spatial distribution of galaxies can only be reported [29]. In 1847, John Herschel found out that the employed for cosmological distances. brightest stars were concentrated in a narrow region on the celestial sphere; later on, in 1879, having studied that 2. Distinctive features of the Solar System and its pattern Benjamin Gould established that the ring was immediate neighbourhood inclined to the plane of the Milky Way at an angle of 18о. That finding refuted the arrangement of the Milky Way There is no clear definition of the immediate solar systematised by the Herschels in the early nineteenth neighbourhood to date. A sphere centred on the Sun thus century. Estimates of distances of the investigated stars ruling out the existence of any star clusters
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