Hansky, Aleksey Pavlovich

(b. Odessa, Russia, 20 July 1870; d. the Crimea, Russia., 11 August 1908)

astronomy.

After completing his studies at the Gymnasium, Hansky entered the Faculty of Physics and Mathematics of Novorossisk University in Odessa (now Odessa University), from which he graduated in 1894. He was then retained at the university to prepare for a career in science. In 1896 he went to St. Petersburg as a probationer at Pulkovo observatory, which was then completing preparations for an expedition to Novaya Zemlya to observe the total solar eclipse of 8 August. Hansky participated actively in this expedition and obtained excellent photographs of the solar corona, which provided him with a beginning for his later research on the form of the solar corona in relation to the phases of solar activity.

To continue his research on the sun, Hansky in 1897 visited Pierre J. Janssen’s observatory at Mont Blanc and the Meudon astrophysical observatory, near Paris. From 1897 to 1905 he made more than ten ascents of Mont Blanc and spent a total of a month and a half at the observatory. He was distinguished by great personal courage: in 1898-1900, in order to observe the Leonids, he made three balloon flights, in Paris and St. Petersburg. In 1901 Hansky participated in an expedition to Spitsbergen, where he made gravimetric measurements under very adverse conditions.

In 1905 Hansky became an astronomer at Pulkovo and a member of the scientific center organized by A.A. Belopolsky at the Academy of Sciences for study of the sun. Also in 1905 he traveled to Spain to observe the solar corona during total solar eclipse. His later expeditions to the Crimea and Central Asia to study zodiacal light stimulated his desire to create in southern Russia, and in the most favorable climatic Conditions, an astrophysical section of the Pulkovo observatory. By chance Hansky learned of the existence in Simeiz, on the southern coast of the existence in Simeiz, on the southern coast of the Crimea, of a modest amateur observatory belonging to N. S. Maltsov and persuaded him to donate it to the pulkovo observatory him to donate it to the branch. Before the organization of the Simeiz section could be completed, Hansky, who had been named its director, drowned. The Simeiz observatory later became famous through the work of Grigory Neuymin (comets and asteroids) and Grigory Shayn (spectra of stars and gas nebulae).

During his short scientific career Hansky studied gravimetry, measuring gravitational force atop Mont Blanc and in the depths of a coal mine on Spitsbergen, conducted research on the zodiacal light, and made observations of Jupiter and the meteors. But his chief service to science was his solar research.

Having Compared his photographs of the solar corona taken during the 1896 eclipse with data on the various phenomena of solar activity over a fifty-year period, Hansky postulated a relation between the form of the solar corona and the number of sunspots, that is, with the phase of solar activity. It appeared that when there is a minimum of spots, the corona is stretched along the plane of the solar equator but is scarcely observable at the poles, and its total luminosity is only slightly greater than the luminosity of the full moon. But during the period of maximum sunspots the corona is ten times brighter than the full moon and is rather evenly distributed on all sides of the solar disk. During later eclipses Hansky’s predictions of the form of the corona were fully confirmed.

While on an ascent of Mont Blanc, Hansky attempted to determine the so-called solar constant (the quantity of ray energy crossing one square centimeter of surface set perpendicular to the solar rays outside the earth’s atmosphere, that is, at a distance of one astronomical unit from the sun). He obtained a somewhat excessive value, but this was the first determination in scientific history. The problem was not successfully resolved until C. G. Abbot’s determination of the solar constant ten years later. Hansky persistently sought a method of photographing the corona without waiting for an eclipse. Thus, in 1898 he fitted to the thirty-centimeter refractor at Janssen’s observatory a special instrument to reduce the brightness of the sky by means of which he covered the solar disk with a metal circle and used a light filter that allowed only red rays to pass through. A fully satisfactory out-of-eclipse coronagraph was not obtained until 1931, by Bernard Lyot.

At Pulkovo, Hansky had striking success in photographing sunspots and details of solar granulation; only in the 1960’s, with the launching of telescopes on special balloons, have better photographs been obtained. According to Hansky’s research, the granules appeared to be very short-term phenomena, sometimes changing beyond recognition within a few seconds. He determined their size (diameters about one second of arc, i.e., up to thousands of kilometers). The granules provided information on the instability of the photosphere and the origins of the flow of hotter substances of the lower photosphere. Hansky noted the connection between the coronal rays and the protuberances and determined the velocity of movement of the substances in the coronal rays (about thirty kilometers per second) and in the protuberances (about 200 kilometers per second).

BIBLIOGRAPHY

I. Original Works. Hansky’s principal works include: “Die totale Sonnenfinsternis am 8 August 1896. Über die Corona und den Zusammenhang zwischen ihrer Gestaltung und anderen Erscheinungsformen der Sonnentätigkeit,” in Izvestiya Imperatorskoi akademii nauk, 6 , no. 3 (1897), 251-270; “Sur la détermination de la pesanteur au sommet du Mont-Blanc à à Meudon,” in Comptes rendus de l‘Acaémie des sciences, 127 (1898), 942-945; “Issledovanie 30-dyuymovogo obektiva Pulkovskoy observatorii po sposobu Gartmana” (“The Examination of the Pulkovo Observatory 30-Inch Objective by Hartmann’s Method”), ibid., 20 , no. 2 (1904), 77-92; “Sur la grande période de l‘activité solaire,” ibid., 20 , no. 4 (1904), 145-148; Intensité de la pesanteur. Missions scientifiques au Spitzberg, l Géodésie, 5-ème Section (St. Petersburg, 1905); “Observations de l‘éclipse totale du Soleil du 30 août 1905,” in Mitteilungen der Nikolai-Hauptsternwarte zu Pulkowo, 1 , no. 10 (l906), 121-136; “Études des photographies de la couronne solaire,” ibid., 2 , no. 19 (1907), 107-118; “Bemerkungen ü das Zodiakallicht,” ibid., 99; “Mouvements des granules sur la surface du soleil,” ibid., 3 , no. 25 (1908), 1-20; and “O dvizhenii veshchestva v korone solntsa” (“On the Movements of Matter in the Solar Corona”), in Izvestiya Russkago astronomicheskago obshchestva, pt. 13, no. 9 (1908), 295-304.

II. Secondary Literature. Papers by O. A. Baklund, G. A. Tikhov, and V. V. Akhmatov on the life and scientific activity of Hansky with a list of his scientific papers are in Izvestiya Russkago astronomicheskago obshchestva, pt. 14, no. 7 (1908), 232-249. See also Y. G. Perel, Vydayushchiesya russkie astronomy (“Outstanding Russian Astronomers,” Moscow, 1951), 194-211; G. A. Tikhov, “A. Hansky (Necrologe),” in Bulletin de la Société astronomique de France, 22 (l908), 421, 461, with portrait; the article on Hansky in Bolshaya sovetskaya entsiklopedia (“Great Soviet Encyclopedia”), X, 2nd ed. (Moscow, 1952), 211; and an obituary in American Journal of Science, 26 (1908), 404.

P. G. Kulikovsky