Interplanetary Complex Research Articles

Comets of the Marsden and Kracht groups

Abstract Perihelion distances of Marsden and Kracht group comets fall into the range 6RS < q < 12RS (the Meyer group comets also share the same perihelion interval). It is by several folds larger than the perihelion distance of the Kreutz group comets (q < 2RS). Average circulation period for comets of the Marsden group is P = 5.5 years and for the Kracht group is P =5.3 years. The Marsden and Kracht group comets share the same origin; as well as 96P (Machholz), object 196256 (2003 EH1), meteor showers the Daytime Arietids, Northern and Southern δ Aquariids, Quandrantids forming the Machholz interplanetary complex. This work offers computational movement simulation for comet-progenitor fragments. It is shown that the orbits of the representatives of the complex can be explained if the decay of the cometprogenitor for objects 96P and 196256 occurred ~9500 years ago. The following evolution direction has been demonstrated for the complex objects: progenitor comet - comet 96P - the Marsden group comets - the Kracht group comets - the Southern δ Aquariids. However, not all the complex objects will necessarily pass through every stage of the above as it can be preceded by the total disintegration of the object.

The age and the probable parent body of the daytime arietid meteor shower

The daytime Arietid meteor shower is active from mid-May to late June and is amongst the strongest of the annual meteor showers, comparable in activity and duration to the Perseids and the Geminids. Due to the daytime nature of the shower, the Arietids have mostly been constrained by radar studies. The Arietids exhibit a long-debated discrepancy in the semi-major axis and the eccentricity of meteoroid orbits as measured by radar and optical surveys. Radar studies yield systematically lower values for the semi-major axis and eccentricity, where the origin of these discrepancies remain unclear. The proposed parent bodies of the stream include comet 96P/Machholz [McIntosh, B.A., 1990. Comet P/Machholz and the Quadrantid meteor stream. Icarus 86, 894 299–304. doi:10.1016/0019-1035(90)90219-Y.] and more recently a member of the Marsden group of sun-skirting comets, P/1999 J6 [Sekanina, Z., Chodas, P.W., 2005. Origin of the Marsden and Kracht Groups of Sunskirting 922 Comets. I. Association with Comet 96P/Machholz and Its Interplanetary Complex. ApJS 923 161, 551–586. doi:10.1086/497374.].In this work, we present detailed numerical modelling of the daytime Arietid meteoroid stream, with the goal to identifying the parent body and constraining the age of the stream. We use observational data from an extensive survey of the Arietids by the Canadian Meteor Orbit Radar (CMOR), in the period of 2002–2013, and several optical observations by the SonotaCo meteor network and the Cameras for All-sky Meteor Surveillance (CAMS).We find the most plausible scenario to be that the age and the formation mechanism of the Arietids is consistent with continuous cometary activity of 96P/Machholz over a time interval of ≈12,000 years. The sun-skirting comet P/1999 J6 suggested by [Sekanina, Z., Chodas, P.W., 2005. Origin of the Marsden and Kracht Groups of Sunskirting 922 Comets. I. Association with Comet 96P/Machholz and Its Interplanetary Complex. ApJS 923 161, 551–586. doi:10.1086/497374.] may contribute to the shower, but the comet break up prior to 950 CE they propose does not reproduce all the characteristics of the observed shower.

Origin of the Marsden and Kracht Groups of Sunskirting Comets. I. Association with Comet 96P/Machholz and Its Interplanetary Complex

Of the three major groups of comets approaching the Sun to between 6 and 12 solar radii and discovered with the coronagraphs on board SOHO, we investigate the Marsden and Kracht groups.We call these comets ''sunskirters'' to distinguish them from the Kreutz system sungrazers. Our objective is to understand the origin, history, and orbital evolution of the two groups.

Physical Processes in Comets

The paper discusses physical processes in comets which involve solar and nuclear radial forces that affect the motions of gases and icy grains, gas-phase chemistry very close to the nuclei of large comets near the sun, sublimation of icy grains, dissociation of parent molecules into radicals and of radicals into atoms, and ionization by sunlight and collisions. The composition and dimensions of nuclei are examined along with variations in intrinsic brightness, the nature of volatiles, gas production rates in the coma, characteristics of icy grains in the coma, and the structure of streamers, ion tails, and dust tails. The structure of the coma is described in detail on the basis of spectroscopic observations of several comets. The origin of comets is briefly reviewed together with the relation of comets to earth, the interplanetary complex, and the interstellar medium. Desirable future observations are noted, especially by space missions to comets.

6.5 Final Remarks

My summary will certainly leave out much fine work but will stress a few of the points that impressed me.First, I note remarkable progress since 1967 when I last worried about the interplanetary complex, particularly the new observations from space and of very small particles. I am delighted to see the ground based Zodiacal Light observers, like Weinberg and Dumont, converging on their observations both of polarization and of intensity. The larger particles are clearly the major contributors particularly away from the Sun. This forces the theoreticians and the laboratory people to find out how these larger particles produce the observed polarization including the negative polarization. Theoreticians always can prove the answer when it is known.

Comets, meteors and the interplanetary complex

Comets, meteors and the interplanetary complex