Aristarkh Apollonovich Belopolsky was a prominent Russian astronomer and astrophysicist. He worked in spectroscopy and discovered a number of spectroscopic binaries. 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.
Background
Ethnicity:
Belopolsky father's ancestors were from a Serbian town called Belo Polje.
Aristarkh Apollonovich Belopolsky was born on July 13, 1854, in Moscow, Russian Empire. 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.
Education
Upon graduating from the Gymnasium in 1873, Belopolsky entered Moscow University, graduating from its Faculty of Physics and Mathematics in 1877.
Career
After graduating from Moscow University in 1877, Belopolsky was enlisted by F. A. Bredikhin, director of the Moscow Observatory 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 1891 a 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.
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 a 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 (9h 50m) differs from the period of rotation of the remainder of the surface (9h 55m), 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 body. The second expedition, 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 semi periodic 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 a 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 the 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 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 8 Cephei type - Cepheid variables - led Belopolsky to the discovery of the no coincidence 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 8 Cephei (“An Investigation of the Spectrum of the Variable Star 8 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.
Views
The main area of astrophysics in which Belopolsky worked was the determination of the radial velocity of celestial bodies.
Membership
Belopolsky was a member of the Russian Academy of Sciences and Russian Astronomical Association. In 1901 he became a member of the Italian Association of spectrographists. In 1910 he became a member of the Royal Astronomical Society.