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1

Influence of Water Ice Sublimation Flux on the Change of Cometary Brightness during the Outburs

Wesołowski M.

Acta Astronomica

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2023

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Vol. 73, No. 3

243--258

EN

The paper presents a new approach to determining the amplitude of the change of cometary brightness during its outburst. The proposed method is based on two pillars. The first pillar is the analysis of the influence of the sublimation flux of water ice originating from porous agglomerates on the amplitude of the change of cometary brightness. The second pillar is the analysis of the efficiency of scattering of incident sunlight that occurs on porous agglomerates consisting of water ice, organic matter and dust. The presented considerations use two equations describing the sublimation flux. In the first case, it was assumed that the agglomerates were covered with a thin layer of porous dust, while in the second case, the agglomerates were exposed. Based on numerous numerical tests, the presence of even a thin layer of dust has been found to reduce the sublimation flux, which translates into differences in the change in the brightness of the comet.

2

A New Indirect Method of Determining Density of Cometary Nuclei

Paradowski M. L.

Acta Astronomica

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2022

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Vol. 72, No. 2

141--159

EN

A new indirect method for determining the bulk density of cometary nuclei is presented. This method has been applied to 136 comets taken from the literature. The method uses the calibration function in the form a1=10.88526+3.39275×a2 and the equation logDN=a2-0.13H, where DN is the nucleus' diameter [km], and H is the comets' absolute total magnitude (coma + nucleus). To obtain the nuclear bulk density [kg/m3] the formula d=(6/π)×10a where a=a1-3a2-9 is used. The mean nuclear bulk density of the 136 comets is 520±10 kg/m3. The relationship between the nuclear bulk density and the origin of the comets is found. For the 40 long-period comets the mean density is 470±10 kg/m3, whereas for the 94 short-period comets from Jupiter family it is 540±10 kg/m3. The accuracy of the calibration function is 1.5%.

3

System of Long-Period Comets as Indicator of the Large Planetary Body on the Periphery of the Solar System

Guliyev A. S., Guliyev R. A.

Acta Astronomica

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2019

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Vol. 69, No. 2

177--203

EN

We study some particular aspects of the hypothesis about the existence of a highly inclined massive celestial body at a distance of 250-400 au. The analysis covers 1249 long-period comets (LPCs) observed up to 2017, having q and Q greater than 0.1 au and 30 au respectively. A plane or planes around which the concentration of perihelia occurs have been searched. The search for such planes has been carried out for groups of LPCs, separated by clusters in T (discovery date), e, q, H (absolute magnitude), Q, 1/aori ("original" a), etc. In almost all cases two types of planes or zones have been detected: the first one is very close to the ecliptic, the other one has the parameters: ip=86°, Ωp=271°. According to the tested hypothesis there is a massive perturber at a distance of 250-400 au from the Sun. We show that the number of aphelia and distant nodes of long-period comet orbits within this interval (250-400 au) significantly exceeds the expected value. The distributions of Q and distant comet nodes may signal the presence of a massive perturber near 300 au. We have estimated that the most probable orbital elements of the hypothetical planet are a=339±34 au, e=0.16±0.02, ω=57°±15°, Ω=272.°7±3°, i=86°±2°. To test the stability of such an orbit as well as its influence on other planets, a model of solar system that includes only the Jovian planets and the putative perturber was integrated for 1 billion years, assuming that the mass of the highly inclined perturber is about 10 Earth masses.

4

Fast Geometric Method for Calculating Accurate Minimum Orbit Intersection Distances

Wiśniowski T., Rickman H.

Acta Astronomica

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2013

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Vol. 63, No. 2

293--307

EN

We present a new method to compute Minimum Orbit Intersection Distances (MOIDs) for arbitrary pairs of heliocentric orbits and compare it with Giovanni Gronchi's algebraic method. Our procedure is numerical and iterative, and the MOID configuration is found by geometric scanning and tuning. A basic element is the meridional plane, used for initial scanning, which contains one of the objects and is perpendicular to the orbital plane of the other. Our method also relies on an efficient tuning technique in order to zoom in on the MOID configuration, starting from the first approximation found by scanning. We work with high accuracy and take special care to avoid the risk of missing the MOID, which is inherent to our type of approach. We demonstrate that our method is both fast, reliable and flexible. It is freely available and its source Fortran code downloadable via our web page.

5

Behavior of Jupiter Non-Trojan Co-Orbitals

Wajer P., Królikowska M.

Acta Astronomica

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2012

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Vol. 62, No. 1

113--131

EN

Searching for the non-Trojan Jupiter co-orbitals we have numerically integrated orbits of 3160 asteroids and 24 comets discovered by October 2010 and situated within and close to the planet co-orbital region. Using this sample we have been able to select eight asteroids and three comets and analyze their orbital behavior in a great detail. Among them we have identified five new Jupiter co-orbitals: (241944) 2002 CU147, 2006 S.A.387, 2006 QL39, 2007 GH6, and 200P/Larsen, as well as we have analyzed six previously identified co-orbitals: (118624) 2000 HR24, 2006 UG185, 2001 QQ199, 2004 AE9, P/2003 WC7 LINEAR-CATALINA and P/2002 AR2 LINEAR. (241944) 2002 CU147 is currently on a quasi-satellite orbit with repeatable transitions into the tadpole state. Similar behavior shows 2007 GH6 which additionally librates in a compound tadpole-quasi-satellite orbit. 2006 QL39 and 2000P/Larsen are the co-orbitals of Jupiter which are temporarily moving in a horseshoe orbit occasionally interrupted by a quasi-satellite behavior. 2006 S.A.387 is moving in a pure horseshoe orbit. Orbits of the latter three objects are unstable and according to our calculations, these objects will leave the horseshoe state in a few hundred years. Two asteroids, 2001 QQ199 and 2004 AE9, are long-lived quasi-satellites of Jupiter. They will remain in this state for a few thousand years at least. The comets P/2002 AR2 LINEAR and P/2003 WC7 LINEAR-CATALINA are also quasi-satellites of Jupiter. However, the non-gravitational effects may be significant in the motion of these comets. We have shown that P/2003 WC7 is moving in a quasi-satellite orbit and will stay in this regime to at least 2500 year. Asteroid (118624) 2000 HR24 will be temporarily captured in a quasi-satellite orbit near 2050 and we have identified another one object which shows similar behavior - the asteroid 2006 UG185, although, its guiding center encloses the origin, it is not a quasi-satellite. The orbits of these two objects can be accurately calculated for a few hundred years forward and backward.

6

2060 Chiron - Chaotic Dynamical Evolution and its Implications

Gabryszewski R.

Acta Astronomica

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2002

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Vol. 52, No. 3

305--216

EN

2060 Chiron - one of the Centaurs orbiting chaotically among the giant planets - is treated as an asteroid and a comet (95P/Chiron) as well. Since the day of the discovery many papers have discussed its past and future fate. In this paper a possibility of Chiron's dynamical evolution to different cometary orbital types is studied. An ensemble of orbital elements was used to describe Chiron's dynamics in terms of probability. The ensemble was generated using a unique scheme of elements creation. Dispersion of elements obtained by this method is much smaller compared to ranges obtained by varying the original elements in the ellipsoid of their mean errors. The chaos in Chiron's dynamical evolution can be seen in 5 to 9 kyrs, although the dispersion of orbital elements is small. Halley type orbits are the rarest noticed orbital types but the number of these objects is three times greater than the number of apparent Halley type comets. The variations of probability of different cometary orbits as a function of time is also presented. The rate of HTC orbit production is only four times lower than the production rate of JFCs after the first 50 kyrs of integration. Remarks on the small body transportation mechanisms are also included.

7

Prediction of the Motion of Asteroids and Comets Over Long Intervals of Time

Włodarczyk I.

Acta Astronomica

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2001

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Vol. 51, No. 4

357--376

EN

Difference of the mean anomalies of two starting orbits of a minor planet or a comet which only differ by an error of calculating of one of the orbital elements grows rapidly with time. This means that it is almost impossible to predict behavior of minor planets or comets on the orbit outside the period of time called the time of stability in our work. The time of stability for some selected minor planets and comets are given. For some minor planets and comets the time of stability is surprisingly short, about several hundreds years only.