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Wlodarczyk I.,Chorzow Astronomical Observatory
Solar System Research | Year: 2012

We show how to calculate the impact orbits of dangerous asteroids using the freely available the OrbFit software, and compare our results with impact orbits calculated using Sitarski's independent software (Sitarski, 1999; 2000; 2006). The new method is tested on asteroid 2009 FJ. Using the OrbFit package to integrate alternate orbits along the line of variation (Milani et al., 2002; 2005a; 2005b), we identify impact orbits and can plot paths of risk for the Earth or any other body in the Solar System. We present the orbital elements of asteroid 2009 FJ and its ephemerides, along with uncertainties, for the next 100 years. This paper continues a long-term research program on impact solutions for asteroids (Wlodarczyk, 2007; 2008; 2009). © 2012 Pleiades Publishing, Ltd.

Cernis K.,Vilnius University | Zdanavicius J.,Vilnius University | Wlodarczyk I.,Chorzow Astronomical Observatory | Stonkute E.,Vilnius University
Baltic Astronomy | Year: 2012

A project devoted to astrometric and photometric observations of asteroids at the Mole̊tai Observatory is described. One of its most important results is the discovery of the asteroid 2010 BT3 belonging to the Amor group of the near-Earth objects. The results of astrometrie and photometric observations of the asteroid are presented. The brightness variations of the asteroid are found to be about 0.2 mag in R. The orbit of the asteroid was computed from 96 observations. This orbit, combined with the apparent brightness, gives the absolute magnitude 21.34 mag and the diameter between 160 m and 360 m, taking albedos of S-type and C-type asteroids, respectively.

Cernis K.,Vilnius University | Boyle R.P.,Vatican Observatory Research Group | Laugalys V.,Vilnius University | Wlodarczyk I.,Chorzow Astronomical Observatory
Baltic Astronomy | Year: 2012

A project for astrometric and photometric observations of asteroids at Mt. Graham Observatory with the VATT telescope is described. One of the most important results is a discovery of the Centaur 2012 DS85. Astrometrie and photometric data on the asteroid are presented. The orbit of the asteroid was computed from 67 observations. Combined with its apparent brightness, the orbit gives an absolute magnitude of 9.43. Using a typical albedo value of 0.08 for Centaurs and TNOs (Moullet et al. 2011), we get a diameter of 2012 DS85 at about 61 km.

Leliwa-Kopystynski J.,University of Warsaw | Wodarczyk I.,Chorzow Astronomical Observatory | Burchell M.J.,University of Kent
Icarus | Year: 2016

A model of impact disruption of the bodies with sizes from the laboratory scale to that of an order of 100km is developed. On the lowermost end of the target size the model is based on the numerous laboratory data related to the mass-velocity distribution of the impact produced fragments. On the minor-planets scale the model is supported by the data related to the largest observed craters on small icy satellites and on some asteroids (Leliwa-Kopystynski, J., Burchell, M.J., Lowen, D. [2008]. Icarus 195, 817-826). The model takes into account the target disruption and the dispersion of the impact produced fragments against the intermolecular forces acting on the surfaces of the contacts of the fragments and against self-gravitation of the target. The head-on collisions of non-rotating and non-porous targets and impactors are considered. The impactor delivers kinetic energy but its mass is neglected in comparison to mass of the target. For this simple case the analytical formulae for specific disruption energy as well as for specific energy of formation of the largest craters are found. They depend on a set of parameters. Of these the most important (i.e. with the greatest influence on the final result) are three rather weakly known parameters. They are: (i) The exponent γ in the distribution function of the fragments. (ii) The characteristic velocity v0 that appears in the velocity distribution of the ejected fragments. (iii) The exponent β in the mass-velocity distribution. The influence of the choice of the numerical values of these parameters on the final results has been studied. Another group of parameters contains the relevant material data. They are: (a) The energy σ of breaking of the intermolecular bonds of the target material per unit of the fragment surface and (b) the density ρ of the target. According to our calculations the transition between the strength regime and the gravitational regime is in the range of the target radius from ~0.4km to ~4km. This estimate holds within a large range of parameters.An application of the results for impact cratering and/or for disruption of satellites and asteroids requires data concerning the impactor energy. We have considered rocky-rocky impacts (an asteroid on an asteroid) and icy-icy impacts (a satellite impacted by a comet). Hypothetical impacts onto some particular asteroids and satellites are discussed as examples. © 2016 Elsevier Inc.

Wlodarczyk I.,Chorzow Astronomical Observatory
Bulgarian Astronomical Journal | Year: 2015

Third of the most interesting potentially dangerous asteroids, after (99942) Apophis and (101955) Bennu, is 2009 FD. We computed impact solutions of the asteroid 2009 FD based on its 296 optical observations from 2009 February 24.36493 UTC to 2014 April 02.15110 UTC, and 1 radar observation from 2014 April 07 20:21:00 UTC. We used the freely available OrbFit Software Package and studied the orbit of 2009 FD forward in the future searching for close approaches with the Earth and for possible impacts up to 2201. Possible impact solutions were computed using the JPL DE405 planetary and lunar ephemerides taking into account the different A2 non-gravitational parameter in the motion of the asteroid 2009 FD. We computed possible impacts in 2185, 2186, 2191, 2192, 2194, 2196 and 2198. They are possible only with the non-gravitational parameter, A2 in the range (-46.0, 0)×10−15au/d2, with the gap between (-25.0, -11.0)×10−15au/d2. It denotes that if A2 is greater than +0.0×10−15au/d2, or smaller than –46.0×10−15au/d2 than impacts with the Earth, are excluded. They are possible with the non-gravitational parameter, A2<=0. It implies that impacts are possible if 2009 FD rotates in retrograde direction. © 2015, Bulgarian Astronomical Journal. All rights reserved.

Wlodarczyk I.,Chorzow Astronomical Observatory
Physics Research International | Year: 2014

We computed impact solutions of the potentially dangerous asteroid (101955) Bennu based on 569 optical observations from September 11.40624 UTC, 1999 to January 20.11189 UTC, 2013, and 29 radar observations from September 21, 1999, through September 29, 2011. Using the freely available OrbFit software package, we can follow its orbit forward in the future searching for close approaches with the earth, which can lead to possible impacts up to 2200. With the A2 nongravitational parameter in the motion of the asteroid (101955) Bennu we computed possible impact solutions using different JPL planetary and lunar ephemerides and different number of additional massive perturbed asteroids. The possible impact path of risk for 2175 is presented. Additionally, we computed possible impact solutions using the normal places method of the selection of Bennu's astrometric observations. Moreover, we computed time evolution of the mean orbital elements and the orbital nodes of Bennu 5 kyr in the backwards and 1 kyr in the future using the Yarkovsky effects. We computed the mean motion and secular orbital resonances of the Bennu. We also computed the influence of the JPL planetary and lunar ephemerides DE403, DE405, DE406, DE414, and DE423 on the close approaches of the asteroid (101955) Bennu with the earth. © 2014 I. Włodarczyk.

Wlodarczyk I.,Chorzow Astronomical Observatory
Acta Astronomica | Year: 2015

The asteroid (410777) 2009 FD is placed at the top of the JPL NASA Sentry Risk Table. We show that the predicted probability of the potential impact of the asteroid (410777) 2009 FD in fact depends on (i): used methods of selection and weighing of observational data, (ii): adopted dynamical model with included non-gravitational effects in the motion of asteroid based on cometary approach, and considerably weaker depends on (iii): the used model of the Solar System with different number of massive asteroids as potential perturbers. We computed impact solutions of the asteroid (410777) 2009 FD based on its 296 optical observations from February 24, 2009 to April 02, 2014 and one radar observation from April 07, 2014. We used the freely available ORBFIT Software Package and studied the future evolution of the orbit of (410777) 2009 FD searching for close approaches with the Earth and for the possible impacts up to the year 2200. According to our study the impacts are possible in the years: 2185, 2186, 2190, 2191, 2192, 2194, 2196, and 2198, provided the non-gravitational parameter A2 in the range of (-46.0,+3.0)×10-15 a.u./d2, with the gap between (-25.0,-11.0)×10-15 a.u./d2.

Wlodarczyk I.,Chorzow Astronomical Observatory | Leliwa-Kopystynski J.,University of Warsaw
Meteoritics and Planetary Science | Year: 2014

The main focus of this paper is calculation of the diameters of asteroids belonging to five families (Vesta, Eos, Eunomia, Koronis, and Themis). To do that, we used the HCM algorithm applied for a data set containing 292,003 numbered asteroids, and a numerical procedure for choosing the crucial parameter of the HCM, called "the cutting velocity" vcut. It was established with a precision as high as 1 m s-1. Thereafter, we used the WISE (Widefield Infrared Survey Explorer) catalog to set a range of albedo for the largest members of each family considered. The albedo data were supported by the data concerning color classification (SDSS MOC4). The asteroids with albedo out of this range were classified as interlopers and were therefore disqualified as family members. Sizes were calculated for the asteroids with albedo within the acceptable range. For the other asteroids (those chosen by means of the HCM, but with albedo not listed in the WISE), the value of albedo of the largest member of the family was adopted. Results are given in a set of figures showing the families on the planes (a, e), (a, i), (e, i). Diameters and volumes of the asteroids that are the individual members of a family were calculated on the basis of their known or assumed albedo and on their absolute magnitude. Volumes of the parent bodies of the families were found on the basis of the cumulative volume distribution of these families. We also studied the secular resonances of the family members. We have shown that the locations of members of the considered asteroid families are related to the lines of secular resonances z1, z2, and z3 with Saturn. © The Meteoritical Society, 2014.

Leliwa-Kopystynski J.,University of Warsaw | Banaszek M.,University of Warsaw | Wlodarczyk I.,Chorzow Astronomical Observatory
Planetary and Space Science | Year: 2012

Craters density distribution versus satellitographical longitude was searched for seven icy satellites: two of Jupiter (Ganymede and Callisto) and five of Saturn (Mimas, Tethys, Dione, Rhea and Iapetus). Craters were classified according to their size. Four bins of the craters diameter were used. Density distributions were found in the longitudinal sectors of the near-equatorial stripes that circumscribe the satellites. The size distributions (R-plots) were done independently for each of the eight longitudinal sectors of the satellites. Searching for the leading/trailing (apex/antapex) and the near-side/far-side asymmetry was done. It was found that the crater density is longitudinally asymmetric for all seven satellites being studied. However, the apexantapex asymmetry is much less pronounced than predicted by theory of Zahnle et al. (2003), for impacts on the satellites by ecliptic comets. We conclude that the impact craters observed on the considered satellites are mostly originated from planetocentric swarm of debris. In that case longitudinal asymmetry is not expected, as stated by Horedt and Neukum (1984a, b). However, cratering longitudinal asymmetry that we observe for Mimas perfectly agrees with calculations of Alvarellos et al. (2005). It is very likely that important part of craters on Mimas were formed due to impacts of ejecta originated from crater Herschel. © 2011 Elsevier Ltd. All rights reserved.

Cernis K.,Vilnius University | Wlodarczyk I.,Chorzow Astronomical Observatory | Eglitis I.,University of Latvia
Baltic Astronomy | Year: 2015

The paper presents statistics of the asteroids observed and discovered at the Baldone Observatory, Latvia, in 2008-2013 within the project for astrometric observations of the near-Earth objects (NEOs), the main belt asteroids and comets. CCD observations of the asteroids were obtained with the 0.80/1.20 m, f/3 Schmidt telescope and a ST-10XME 15×10 mm CCD camera. In the Minor Planet Circulars and the Minor Planet Electronic Circulars (2008-2013) we published 3511 astrometric positions of 826 asteroids. Among them, 43 asteroids were newly discovered at Baldone. For 36 of these asteroids the precise orbits are calculated. Because of short observational arc and small number of observations, a few asteroids have low-precision orbits and their tracks have been lost. For seven objects with poorly known orbits we present their ephemerides for 2015-2016. The orbits and the evolution of orbital elements of two asteroids, (428694) 2008 OS9 from the Apollo group and the Centaur (330836) Orius (2009 HW77), are recalculated including new observations obtained after 2011.

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