scholarly journals 8. Comet Halley and Nongravitational Forces

1977 ◽  
Vol 39 ◽  
pp. 61-64
Author(s):  
D. K. Yeomans
Keyword(s):  
Force Model ◽  
Water Ice ◽  
Comet Halley ◽  
Nongravitational Effects ◽  
Nongravitational Forces

The motion of Comet Halley is investigated over the 1607-1911 interval. The required nongravitational force model was found to be most consistent with a rocket-type thrust from the vaporization of water-ice in the comet’s nucleus. The nongravitational effects are time-independent over the investigated interval.

scholarly journals The dynamical history of comet Halley

1985 ◽  
Vol 83 ◽  
pp. 389-398
Author(s):  
Donald K. Yeomans
Keyword(s):  
Water Ice ◽  
Direct Rotation ◽  
History Of ◽  
Comet Halley ◽  
Nongravitational Effects ◽  
Nongravitational Forces

AbstractThe history of the attempts to predict the motion of comet Halley is outlined and the importance of the so-called nongravitational forces acting upon this comet is emphasized. Recent orbital work of the International Halley Watch Astrometry Network is reviewed. Comet Halley’s transverse nongravitational parameter is positive and nearly constant with time suggesting that the comet is in direct rotation without precession of the spin pole. The nongravitational effects are consistent with the vaporization of water ice from the comet’s nucleus and long term integrations suggest that the comet has been in its present orbit for at least 16,000 years and probably much longer.

scholarly journals Nongravitational Effects on Comets: the Current Status

1972 ◽  
Vol 45 ◽  
pp. 135-143
Author(s):  
B. G. Marsden
Keyword(s):  
Heliocentric Distance ◽  
Equations Of Motion ◽  
Current Status ◽  
Future Research ◽  
Secular Changes ◽  
Nongravitational Effects ◽  
Nongravitational Forces

A method for allowing for the effects of nongravitational forces on the motions of comets is summarized. Study of the motions of specific comets indicates that these forces act essentially continuously but have a high inverse dependence on heliocentric distance; there is also evidence for secular changes. The equations of motion employed are discussed in terms of the Whipple icyconglomerate model. Nongravitational parameters are tabulated for all 46 comets observed at three or more perihelion passages. We point out the particular problems that still exist for certain comets and suggest directions for future research.

Nongravitational effects on comets: a progress report

1974 ◽  
Vol 22 ◽  
pp. 181-185
Author(s):  
B. G. Marsden
Keyword(s):  
Heliocentric Distance ◽  
Progress Report ◽  
Complete Dissolution ◽  
New Developments ◽  
Nongravitational Effects ◽  
Nongravitational Forces

AbstractNew developments since 1970 are discussed, notably the identification of the comets exhibiting sudden anomalies in their motions with those comets whose nongravitational effects normally increase with time (resulting in the eventual complete dissolution of these comets, rather than conversion into asteroidal objects) and the introduction of a law for the variation of the nongravitational forces with heliocentric distance that is based on the theory of vaporization of ice.

scholarly journals Nongravitational forces on comets: the first fifteen years

1985 ◽  
Vol 83 ◽  
pp. 342-352
Author(s):  
B.G. Marsden
Keyword(s):  
Theoretical Models ◽  
Current Situation ◽  
Nongravitational Effects ◽  
Nongravitational Forces

AbstractThe recent and current situation with regard to our analysis and understanding of the nongravitational effects in cometary motions is reviewed. Comets can be categorized according to the different physical situations that may exist in their nuclei. Further experimentation with theoretical models and empirical fits to observations is encouraged.

3 micron spectrophotometry of Comet Halley - Evidence for water ice

1988 ◽  
Vol 334 ◽  
pp. 1044 ◽  
Author(s):  
Jesse D. Bregman ◽  
A. G. G. M. Tielens ◽  
Fred C. Witteborn ◽  
David M. Rank ◽  
Diane Wooden
Keyword(s):  
Water Ice ◽  
Comet Halley

scholarly journals Some Remarks on the Liberation of Gases from Cometary Nuclei

1972 ◽  
Vol 45 ◽  
pp. 260-264
Author(s):  
B. Yu. Levin
Keyword(s):  
Total Mass ◽  
Physical Theory ◽  
Point Of View ◽  
Reactive Force ◽  
Cometary Nuclei ◽  
Water Ice ◽  
Total Mass Loss ◽  
Order Of Magnitude ◽  
Perihelion Passage ◽  
Nongravitational Forces

According to modern data water ice is the main constituent of cometary nuclei. The rate of its evaporation determines the rate of liberation of other constituents, including those that determine the photometric properties of comets. The estimates of the total mass loss per perihelion passage seem to give values about one order of magnitude smaller than those necessary to explain the nongravitational forces as due to the reactive force of material leaving the nuclei. Thus the conventional explanation of the nongravitational forces deserves further study from the point of view of the physical theory of comets.

scholarly journals Nongravitational Forces on Comets

1976 ◽  
Vol 25 (Part1) ◽  
pp. 465-489
Author(s):  
B. G. Marsden
Keyword(s):  
Average Period ◽  
Nongravitational Effects ◽  
Nongravitational Forces ◽  
The Revolution

The study of the nongravitational effects on comets began slightly more than a century and a half ago. As is well known, Encke (1819) demonstrated that comet 1819 I had a revolution period of not more than a few years and that the same comet had also been observed in 1786, 1795 and 1805. The observations clearly required that the revolution period be about 3.3 years, and Encke went on to remark that, after approximate allowance had been made for the perturbations by the planets, the average revolution period seemed to be 1207.9 days between 1795 and 1805, but only 1207.3 days between 1805 and 1819. As a result of a more refined computation of the planetary perturbations, the following year he (Encke 1820) was able to confirm these figures and find in addition that the average period between 1786 and 1795 was as much as 1208.1 days.

scholarly journals An Investigation of the Motion of Periodic Comet Borrelly from 1904 to 1967

1972 ◽  
Vol 45 ◽  
pp. 190-194 ◽  
Author(s):  
L. M. Belous
Keyword(s):  
Mean Error ◽  
Secular Acceleration ◽  
Periodic Comet ◽  
Nongravitational Effects ◽  
Nongravitational Forces

The motion of P/Borrelly has been investigated using all precise published positions and taking into account the perturbations by Venus to Pluto. Nongravitational forces have been found to influence the motion of the comet considerably, formerly as a secular deceleration, more recently as a secular acceleration. By linking the seven apparitions 1904–1960, with allowance for the nongravitational effects, we have obtained a set of elements which represents 802 observations with a mean error of 1′.89.

Models of comets with strongly variable nongravitational effects

1999 ◽  
Vol 173 ◽  
pp. 381-387
Author(s):  
M. Królikowska ◽  
G. Sitarski ◽  
S. Szutowicz
Keyword(s):  
Cometary Nucleus ◽  
Spin Axis ◽  
Reactive Force ◽  
Orbital Elements ◽  
Cometary Nuclei ◽  
Short Period ◽  
Basic Parameters ◽  
Polar Radius ◽  
Cometary Activity ◽  
Nongravitational Effects

AbstractThe nongravitational motion of five “erratic” short-period comets is studied on the basis of published astrometric observations. We present the precession models which successfully link all the observed apparitions of the comets: 21P/Giacobini-Zinner, 31P/Schwassmann-Wachmann 2, 32P/Comas Solá, 37P/Forbes, and 43P/Wolf-Harrington. We used the Sekanina's forced precession model of the rotating cometary nucleus to include the nongravitational terms into equations of the comet's motion. Values of six basic parameters (four connected with the rotating comet nucleus and two describing the precession of spin-axis of the nucleus) have been determined along the orbital elements from positional observations of the comets. The solutions were derived with additional assumptions which introduce instantaneous changes of modulus of reactive force,Aand of maximum of cometary activity with respect to perihelion time. The present precession models impose some contraints on sizes and rotational periods of cometary nuclei. According to our solutions the nucleus of 21P/Giacobini-Zinner with oblateness along the spin-axis of about 0.32 (equatorial to polar radius of 1.46) is the most oblate among five investigated comets.

Hydrogen Cyanide Polymers from the Impact of Comet P/Shoemaker-Levy 9 on Jupiter

1997 ◽  
Vol 161 ◽  
pp. 179-187
Author(s):  
Clifford N. Matthews ◽  
Rose A. Pesce-Rodriguez ◽  
Shirley A. Liebman
Keyword(s):  
Amino Acids ◽  
Solar System ◽  
Hydrogen Cyanide ◽  
Nitrogen Heterocycles ◽  
Laboratory Studies ◽  
Heterogeneous Solids ◽  
The Many ◽  
Comet Halley ◽  
The Impact ◽  
By Products

AbstractHydrogen cyanide polymers – heterogeneous solids ranging in color from yellow to orange to brown to black – may be among the organic macromolecules most readily formed within the Solar System. The non-volatile black crust of comet Halley, for example, as well as the extensive orangebrown streaks in the atmosphere of Jupiter, might consist largely of such polymers synthesized from HCN formed by photolysis of methane and ammonia, the color observed depending on the concentration of HCN involved. Laboratory studies of these ubiquitous compounds point to the presence of polyamidine structures synthesized directly from hydrogen cyanide. These would be converted by water to polypeptides which can be further hydrolyzed to α-amino acids. Black polymers and multimers with conjugated ladder structures derived from HCN could also be formed and might well be the source of the many nitrogen heterocycles, adenine included, observed after pyrolysis. The dark brown color arising from the impacts of comet P/Shoemaker-Levy 9 on Jupiter might therefore be mainly caused by the presence of HCN polymers, whether originally present, deposited by the impactor or synthesized directly from HCN. Spectroscopic detection of these predicted macromolecules and their hydrolytic and pyrolytic by-products would strengthen significantly the hypothesis that cyanide polymerization is a preferred pathway for prebiotic and extraterrestrial chemistry.

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