Belopolsky, Aristarkh Apollonovich

(b. Moscow, Russia, 13 July 1854; d. Pulkovo, U.S.S.R., 16 May 1934)

astrophysics.

Belopolsky was born into an intellectual but poor family; his father, Apollon Grigorievich, a teacher in a Gymnasium, had not graduated from the Faculty of Medicine at the University of Moscow because of a lack of funds. His mother, the daughter of a doctor, taught music in Moscow. Upon graduating from the Gymnasium in 1873, Belopolsky entered Moscow University, graduating from its Faculty of Physics and Mathematics in 1877.

F . A. Bredikhin, director of the Moscow Observatory, enlisted Belopolsky to work there on photographing the sun. Belopolsky thus became seriously interested in and decided to devote himself to astronomy. In 1879 he was named a supernumerary assistant at the observatory.

An investigation of the photographs that he had taken of the sun served as the topic of Belopolsky’s master’s thesis, “Pyatna na solntse i ikh dvizhenie” (“Spots on the Sun and Their Movements,” 1886). In 1888 Belopolsky was appointed a junior assistant in astronomy at the Pulkovo Observatory, and in 1891a staff astrophysicist. He was elected an extraordinary academician in 1903 and ordinary academician in 1906. From 1908 to 1916 he was the vice–director of Pulkovo Observatory, from 1917 to 1919 its director, and from 1933 its honorary director.

During his eleven years at Moscow Observatory, in addition to his photographic work, Belopolsky measured on the meridional circle the precise positions of a selected group of stars, planets, and asteroids, and the positions of comets. Besides systematically photographing the sun and studying the law of its rotation, Belopolsky was the first in Russia to attempt to photograph stars; he achieved notable success with low-sensitivity bromide plates, photographing stars up to magnitude 8.5. He photographed the total solar eclipse of 1887, at which time he obtained on one negative a photograph of the internal solar corona, taken simultaneously by four separate objectives.

The main area of astrophysics in which Belopolsky worked was the determination of the radial velocity of celestial bodies. The application of photography to the study of their spectra had much significance for the development of astrophysics at the end of the nineteenth century. Belopolsky built spectrographs and was a tireless observer who used these devices in conjunction with all the powerful refractors at the Pulkovo Observatory.

The first two years of Belopolsky’s stay at Pulkovo were devoted not to astrophysics, however, but to astrometrical observation, using a transit instrument, and to the working up of prior observations by August Wagner, from which he obtained reliable parallaxes for a number of bright stars (1889). Only in 1891, after Bredikhin became director at Pulkovo, did Belopolsky’s active and fruitful career in astrophysics begin. Belopolsky reestablished the abandoned astrophysics laboratory and ordered from the observatory’s workshops several spectrographs, which he himself helped to build. He was the first to use dry photographic plates, instead of the previously used colloidal plates. Belopolsky quickly became, with Scheiner and Fogel of Potsdam, a leading specialist in solar and laboratory spectroscopy. In 1902 he was invited to join the editorial board of the American Astrophysical Journal.

Belopolsky began his spectrographic work in 1895 with a study of the large planets, his goal being to explain the peculiarities of their axial rotation. It turned out that the angular rate of rotation of Jupiter’s equatorial zones is 4-5 percent greater than that at other jovicentric latitudes. This confirmed a conclusion drawn by Belopolsky while he was still in Moscow; in analyzing observations of Jupiter taken over a period of 200 years, he had established that the period of rotation of the planet’s equatorial region (9^h 50^m) differs from the period of rotation of the remainder of the surface (9^h 55^m), which is separated from the equatorial region by two dark bands.

In 1895, using a spectrograph attached to a 30- inch refractor to study the radial velocities of various points on Saturn’s rings, Belopolsky brilliantly confirmed the theoretical conclusion of James Clerk Maxwell and Sofia V. Kovalevskaya that Saturn’s rings are not solid, but consist of a multitude of small satellites. In addition, he found that the spectrum of the ring was rich in ultraviolet rays, which he explained as the influence of the planet’s atmosphere on the spectrum of the planet itself.

At Pulkovo he continued his study of the sun’s surface, but he shifted from a study of the sun’s rotation by observing its faculae—the method he himself had proposed—to systematic observations of its protuberances and eruptions and, later, to a study of the movements of matter within the sun, a problem that is still important. Belopolsky also studied the fine structure of spectral lines and their changes in shape over time.

In 1904 Belopolsky joined the International Union for Cooperation in Solar Research, organized by G. E. Hale. In Russia there was a branch of the Union, the Commission for the Investigation of the Sun, to which many eminent physicists and astronomers belonged. The Union decided to undertake an eleven-and-a-half–year study of the sun, and for this work Belopolsky ordered a special three–prism spectrograph. In 1915 he published Russia’s first study in spectrophotometry. “O temperature solnechnykh pyaten” (“On the Temperature of Sunspots”), in which he obtained a temperature of 3,500° C. for these spots. This has been confirmed by the latest investigations.

Belopolsky participated in two more expeditions to observe solar eclipses. In 1896 he succeeded in determining from the inclination of the spectral lines in the spectrum of the solar corona that the corona does not rotate like a solid bidy. The second expendition, in 1907, was not successful because of bad weather.

The study of star spectra on the basis of the Doppler principle was begun with the effective determination of the rate of expansion of the shell of Nova Aurigae, which appeared in 1892; Belopolsky conducted investigations of the spectra of Nova Persei (1901), which manifested semiperiodic fluctuations and changes in its spectrum, as well as of Nova Geminorum (1912), Nova Aquilae (1918), Nova Cygni (1920), and several others.

Belopolsky began studying the spectra of common (i.e., not new) stars in 1890, primarily to measure their radial velocities, and gave special attention to spectroscopic binary stars. He discovered the spectral duality of many stars, especially the star α Lyrae, which, until then had been considered a standard star in all catalogs of radial velocities. For the majority of spectroscopic binary stars he studied, Belopolsky determined the elements of their orbits and, in a number of cases, their changes. These changes of the elements attested to the presence of a third component in these systems (for example, Algol’s third component and the polestar’s third component).

Belopolsky discovered the variability of the spectrum of α₂ Canum Venaticorum, which bespoke strong and irregular changes in the atmosphere of this star, the prototype of a special class of stars with strong perturbations in their atmospheres.

A study of the spectra of stars of the δ Cephei type—Cepheid variables—led Belopolsky to the discovery of the noncoincidence of the phases of changes in brightness and changes of radial velocities, as well as the discovery of periodic changes in the intensity of absorption lines. Belopolsky’s determination of the parallaxes and linear dimensions of several visual binary stars is also of interest. It is worth noting that in 1896, at Belopolsky’s defense of his doctoral dissertation, Issledovanie spektra peremennoy zvezdy δ Cephei (“An Investigation of the Spectrum of the Variable Star δ Cephei”), the physicist N. A. Umov first explained the periodic changes of radial velocity (observed by Belopolsky) by the hypothesis of an individual star’s pulsation. The pulsation theory of Cepheids was not completely developed until the work of the Soviet astrophysicist S. A. Zhevakin.

Belopolsky’s laboratory investigations occupy a special place in the history of science. In his master’s thesis, as a supplement to the theoretical analysis of the laws of motion of solar matter, Belopolsky conducted an original experiment using a glass flask filled with water, in which were suspended minute particles of stearin. A coordinate grid plotted on the surface of the flask facilitated registration of the behavior of the stearin particles, which revealed the particularities of the liquid’s rotation. The angular velocity of the rotation declined monotonically from the equator to the latitude of 55°, while the meridional velocity increased up to this same latitude, recalling the corresponding particularities of the rotation of elements of the sun’s surface.

His verification of the validity of Doppler’s principle in optics is considered a classic. For this experiment Belopolsky constructed an exceedingly original device in which, by means of the multiple reflections of a beam of light between two oppositely rotating “water wheels” whose blades were strips of plane mirrors, he succeeded in obtaining a speed of the image’s motion on the order of 1 km./sec., which was capable of being measured with the sufficient certainty to verify the Doppler principle convincingly.

BIBLIOGRAPHY

1. Original Works. Belopolsky’s major writings are “Pyatna na solntse i ikh dvizhenie” (”Spots on the Sun and Their Movements”), master’s thesis (University of Moscow, 1886); “Issledovanie smeshchenia liniy v spektre Saturna i ego koltsa” (“An Investigation of the Shift of Lines in the Spectrum of Saturn and of Its Ring”), in Izvestiya Imperatorskoi akademii nauk, 3 (1895); Issledovanie spektra peremennoy zvezdy δ Cephei (“An Investigation of the Spectrum of the Variable Star δ Cephei”; St. Petersburg, 1895); “O zvezde α’ Bliznetsov kak spektralno-dvoynoy” (“On the Star α’ Geminorum as a Spectral-Binary Star”), in Izvestiya Imperatorskoi akademiinauk, 7, no. 1 (1897); “Opyt issledovania printsipa Doplera-Fizo, ne pribegaya k kosmicheskim skorostyam” (“An Attempt to Investigate the Doppler-Fizo Principle, Without Resorting to Cosmic Velocities”), ibid., 13 , no. 5 (1900), 461–474; “O vrashcheny Yupitera” (“On the Rotation of Jupiter”), ibid., 6th ser., 3 (1909); “Avtobiografia” (“Autobiography”), in Materialy dlya biograficheskogo slovarya deystvitelnykh chlenov Akademii nauk. 1889–1914, chast pervaya, I (Petrograd, 1915), pp. 121–122; “O spektre Novoy 1918 g. (predvaritelnoe soobshchenie)” (“On the Spectrum of the Nova of 1918 [Preliminary Report]”). in Izvestiya Imperntorskoi akademii nauk;Astrospektroskopia (“Astrospectroscopy”; Petrograd, 1921); “Comets and lonization.” in Observatory. 46 (1923), 124–125; “Über die Intensitätsveränderlichtkeit der Spektrallinien einiger Cepheiden.” in Izvestiya Puylkovo Obs., 2nd ser., 2 , no. 101 (1927), 79–88; “Ob izmeny intensivnosti liny v spektrakh nekotorykh tsefeid,” (“On Changes in the Intensity of Lines in the Spectra of Certain Cepheids”), in Izvestiya Akademii nauk, 7th ser., no. 1 (1928): and “Bestimmung der Sonnenrotation auf spektroskopischen Wege in den Jahren 1931, 1932 and 1933 in Pulkovo.” in Zeitschrift für Astrophysik, 7 (1933), 357–363.

II. Secondary Literature. Works on Belopolsky are S. N. Blazhko. “A. A. Belopolsky,”in Bolshaya sovetskaya entsiklopedia, IV (1950), 462–464; V. G. Fesenkov, “Aristarkh Apollonovich Belopolsky,” in Lyudi russkoy nauki(“People of Russian Science”; Mosow, 1961), pp. 185–192; B. P. Gerasimovich, “A. A. Belopolsky. 1854–1934.” in Astronomicheskii zhurnal (SSSR). 2 . pt. 3 (1934), 251–254; O. A. Melnikov, “Aristarkh Apllonovich Belopolsky (1854–1934). Nauchno-biografichesky ocherk” (“Aristarkh Apollonovich Belopolsky [1854–1934]. A Scientific-biographical Essay”). in A. A. Belopolsky. Astronomicheskie trudy (“A. A. Belopolsky. Astronomical Works”; Moscow, 1954). pp. 7–58; Y. G. Perel, Vydayushchiesya russkie astronomy (“Outstanding Russian Asatronomers”; Moscow. 1951). pp. 85–107; K. D. Pokrovsky. “A. A. Belopolsky (k 50-letiyu ego nauchnoy deyatelnosti 1877–1927)” (“A.A. Belopolsky [on the 50th Anniversary of His Scientific Career 1877–1927]”). in Astronomicheskii kalendar na 1928 god (“Astronomical Calendar for 1928”: Nizhni Novgorod, 1927), pp. 123–125, with illustrations: and D. A. Zhukov, “Spisok nauchnykh robat akademika A. A. Belopolskogo 1877–1934” (“A List of the Scientific Papers of Academician A. A. Belopolsky 1877–1934”), in Byulleten’ Komissii po issledovaniya solntsa akademii nauk SSSR. nos. 10–11 (1934), 7–20.

P.G. Kulikovsky