COMETARY INVESTIGATIONS

The physics of comets is another important direction of scientific research at the Institute of Astrophysics, Tajik Academy of Sciences. 

These researches cover all sections of cometary physics and extensive observational and experimental material on comets has been obtained there. In 1955, A.M.Bakharev discovered a comet which became known as the Bakharev-McFarlan-Krienke comet. The expansion of the observational base and the use of telescopes installed in Hissar and Sanglokh observatories allowed photographic, spectroscopic, photoelectric, and polarimetric observations of comets. In the Institute a mechanical theory of cometary forms was developed, and problems of the interaction of corpuscular solar streams with cometary atmospheres have been investigated. A theory of plasma cometary tails was developed and non-stationary processes in comets have been also studied. It was shown that many such processes, for example, cometary outbursts, are associated with the solar activity.
Tajik scientists have also developed a theory of the disintegration of cometary icy nuclei. The thermal regimes of such nuclei were estimated. Theoretical data were tested under laboratory conditions which simulated the cosmic ones. The process of disintegration of the nucleus with dust mantle, the velocities of ejection of mantle fragments, the covering of the nucleus by refractory mantle and so on were studied in the laboratory. It was established that the nuclei of some short-periodic comets develop a refractory mantle and they might evolve into aster-oid-like bodies. The dependence of brightness decrease of short-period comets on their perihelion distance was established.
Polarimetric and colorimetric investigations of comets have revealed negative polarization of the continuum radiation of comets at small phase angles (angle: Sun-comet-Earth), nonlinear growth of cometary brightness in the region of small phaseangles has been found ("oppositional effect"), the theory of shock waves arising from the interaction of magnetized corpuscular solar wind with cometary plasma was worked out. The interaction of interplanetary dust particles with dust particles of the cometary atmosphere is investigated and, a mechanism of X-ray radiation of comets and the appearance of multicharge ions is proposed.
The Institute of Astrophysics of the Tajik Academy of Sciences actively collaborated in working up and in the realization of the International Halley Watch programs. Astrophysical and positional observations of a number of asteroids have been carried out and the orbital evolution of some Near-Earth asteroids associated with meteoroid streams, including the Taurid Complex asteroids, are being investigated.