Lunar and Planetary Science XXXVII (2006) 1134.pdf

NOTES TO IJIRAQ AND KIVIUQ ORBITAL EVOLUTION RECONSTRUCTION. A. E. Rosaev1, 1FGUP NPC "NEDRA" Svobody 8/38, Yaroslavl 150000, Russia,E-mail: [email protected] .

Introduction: The problem of origin of outer Table 2 Main periods for Kiviuq and Ijiraq orbital irregular satellites of large planets is considered. The motion and evolution capture way of their origin most probable, however Kiviuq Ijiraq there is not detail theory. There are a number of P (days) 449.21942 451.46596 irregular satellites, discovered in recent time. It gives Tcon, , yr 245.7±0.2 an ability to investigate the statistics of orbital Pnode, yr 846.46 868.25 interaction and try to reconstruct real collision history Tnode ,yr 32880±30 of these objects. Nesvorny et all [1] research evolution ∆T between two nearest 6 of orbit orientations in asteroid families and prove fact conjunctions at epoch of (8.08±0.01)*10 of recent catastrophic destruction in asteroid main belt. intersections, yr On the other hand, the method of investigations of minimal distance between orbits successfully applied It is evident, that for breakup epoch the distance in our previous works [2]. It is naturally to apply these between orbits must be close to zero, and conjunction two ideas to irregular satellites orbits with close (around longitude of minimal distance) must take elements for determination their parent body possible place. Let breakup take place at epoch t. Next ability to catastrophic destruction epoch. There are few groups exact repeat breakup configuration will take place of irregular satellites in Jupiter and Saturn systems. We through about 33000 years due to mutual node motion restrict this consideration by pair of orbits with close (orbit precession), however, due to long time between elements: Kiviuq and Ijiraq (table 1). subsequent conjunctions (240 years), not each The quasi coorbital objects have a particular configurations is suitable. A very long period between interest. It is natural to suppose, that such close orbits conjunction and orbit configuration repeating for appear not causal, but a product of catastrophic Kiviuq and Ijiraq case (deltaT) means, that we have breakup with small relative velocity. It is evident, that relative small number of similar events (about 500) at breakup process may be related with capture; and this the history of the Solar system and can to consider process could be multistage each more carefully. Due to Yarkovsky effect, close Table 1 Kiviuq and Ijiraq mean orbital elements (R. A. orbits can change their mutual positions, so most Jacobson, private communications) recent cases of close encounters are most possible for

Kiviuq Ijiraq breakup. Moreover, if conjunction takes place close to epoch a 1.1365000 1.1442000 e 0.3336 0.3215 33000 year, according to precession period, it can take

ω 83.043 85.523 place far from longitude of orbit intersection point. It

i 46.148 46.73 means, that the longitude of minimal distance between

Ω 359.519 136.348 orbits must take into account in ∆T value (table 2). The calculations show that really zero encounters between To the Epoch of Ijiraq and Kiviuq Parent Body Saturnian moonlets can take place about one time per Destruction Determination: The studying outer 100 million years. So, we must consider only about 40 natural satellite close orbits rather easy than asteroids cases. by some reasons first of all, the main perturbation from In according with our data, main result of this the Sun change in more narrow range, than Jupiter investigation – a most close to present possible Epoch perturbation for minor planets, and there are no of catastrophic breakup when Kiviuq and Ijiraq appear subsequent encounters with another objects. is 1.938±0.002 *106 yr. The orbital periods and rates of orbit precession are Conclusions: The unique orbital characteristics of given in table 2. The period Tcon between conjunction small irregular Saturn satellites Ijiraq and Kiviuq and period Tnode between two similar orbit provide a very rare mutual close encounters . It is orientations are calculated by expressions: possible to calculate main periods in studied system.

The epoch of most recent close encounter is calculated. Tcon=P /(P -P )*P /365.24 1 2 1 2 References: [1] Nesvorny D., et al. (2002). Nature,

Vol 417, 721. [2] Rosaev A.E. (2001) In: Dynamics of Tnode=Pnode1/(Pnode2 – P node1)*Pnode2 Natural and Artifical Celestial bodies, 301-303. and it was verified by numeric calculations.