112421-01  Hubble, Edwin.
Extra-Galactic Nebulae. (25,5 x 17 cm). 49 S. Mit 1 Tafeln und 3 Abbildungen. Original-Broschur. (Sonderdruck aus: Astrophysical Journal).
(Chicago, University of Chicago Press), 1926.
Erste Ausgabe seines berühmten Klassifizierungssystems für Galaxien. - "Hubble was the first to introduce a significant classification system for galaxies. He presented this at the meeting of the International Astronomical Union at Cambridge, England, in 1925 and it was published the next year in the 'Astrophysical Journal'. This system is the basis of the classification still used. Hubble found that most galaxies showed evidence of rotational symmetry about a dominating central nucleus, although a minority, amounting to not more than 3 percent of those he studied, lacked both these features. He called the two types 'regular' and 'irregular,' respectively. He found that the regular galaxies fell into two main classes - 'spirals' and 'ellipticals' - and that each class contained a regular sequence of forms. One end of the elliptical sequence was found to be similar to one end of the spiral sequence. The spirals were subdivided into two parallel subsequences, normal and barred. The classification was essentially empirical and independent of any assumptions concerning the evolution of galaxies" (DSB). - Hubble (1889-1953) war der Begründer der modernen extragalaktischen Astronomie und der erste, der die Rotverschiebung der Sterne beobachtete und damit den Nachweis für die Expansion des Universums lieferte. - Stempel auf dem Titel. Vorderer Umschlag mit schwachem Knick, sonst gut erhalten. - DSB 6, 529

2.600 €