Motion of the Minor Planet 4179 Toutatis: Can We Predict Its Collision with the Earth?

• Autorzy: Sitarski G.
• Języki publikacji: EN

Abstrakty

EN

Minor planet 4179 Toutatis is an Apollo type object with a very small orbit inclination (i=0°.47), hence it has a possibility to approach closely the Earth (an encounter to within 0.01 a.u. is expected in 2004) and might be a good candidate for a future collision with the Earth. We collected 640 astrometric observations of Toutatis from the period 1934-1997 to improve the orbit. We had to include a nongravitational term into equations of motion expressed by a secular change a of the semi-major axis a of the Toutatis orbit to obtain a fully satisfactory solution of the orbit determination. A value a=-0.16×10^-10 is two orders smaller than that determined in the case of short-period comets with known nongravitational effects. To investigate the long-term motion of Toutatis we numerically integrated the equations of motion by recurrent power series taking into account perturbations caused by the eight planets from Mercury to Neptun, treating the Earth and Moon as separate bodies, and also by the four biggest asteroids. We randomly varied the orbital elements to examine the Toutatis' motion for a number of different orbits. We present a new method of the random orbit selection which allows us to find a set of different orbits but representing well all the observations used for the orbit correction. Our results confirm a conclusion found by other authors that Toutatis orbit is exceptionally chaotic. Therefore, we are not able to predict the motion of Toutatis further than for 300 years. However, our integrations spanning 1500 years showed that the evolution of position of the descending node of Toutatis' orbit might go also in such a direction that the orbits of Toutatis and of the Earth would intersect in the future. Hence a possibility of the Toutatis-Earth collision is not excluded but it is completely unpredictable. To investigate conditions of a hypothetical collision of a minor planet with the Earth we made the following numerical simulation. Based on the Toutatis' orbit we deduced such orbital elements for a fictitious minor planet "Fatum" that a shape of the orbit was very similar to that of Toutatis, but we knew in advance that "Fatum" would certainly collide with the Earth in September 2004 and we calculated values of the impact parameters. We created a set of 638 artificial observations of "Fatum" in 1988-1997 for the same dates and with the same random observational errors like those of Toutatis. Then we corrected the "Fatum's" orbit for different observational intervals to examine the exactness of the impact prediction in 2004. We found that in 1993 we would be sure that the collision is inevitable, and in 1997 we could determine an impact area on the Earth's surface in range of a square of 100×100 km. We show that if we knew the impact date so early we could undertake an action to avoid the collision by trying to change the "Fatum's" heliocentric velocity only by one cm/sec.

Słowa kluczowe

EN

minor planets; asteroids

• Wydawca: Copernicus Foundation for Polish Astronomy
• Czasopismo: Acta Astronomica
• Rocznik: 1998
• Tom: Vol. 48, No. 3
• Strony: 547--561
• Opis fizyczny: Bibliogr. 9 poz., rys., tab., wykr.

Twórcy

autor

Sitarski G.

• Institute of Physics, University in Białystok, Lipowa 41, 15-424 Białystok, Poland
• Space Research Center, Polish Academy of Sciences, Bartycka 18A, 00-716 Warsaw, Poland

Bibliografia

• Bielicki, M., and Sitarski, G. 1991, Acta Astron., 41, 309.
• Bretagnon, P., and Francou, G. 1988, Astron. Astrophys., 202, 309.
• Hudson, R.S., Ostro, S.J. 1995, Science, 270, 84.
• Sitarski, G. 1979, Acta Astron., 29, 401.
• Sitarski, G. 1981, Acta Astron., 31, 471.
• Sitarski, G. 1983, Acta Astron., 33, 295.
• Sitarski, G. 1992, Astron. J., 104, 1226.
• Whipple, A.L., and Shelus, P.J. 1993, Icarus, 105, 408.
• Ziołkowski, K. 1994, Acta Astron., 44, 213.