04/mai/18 -The surviving journey of Thypon-Echidna binary through the planetary region (Rosana Araujo, UNESP)

Trans-Neptunian Objects (TNOs) can evolve to become Centaurs and even Near-Earth Objects (NEOs). The orbital evolution of these bodies is chaotic, full of close planetary encounters that generate instabilities. Among the TNOs there are multiple systems. Today, 81 Trans-Neptunian Binaries (TNBs) are known. From those, there are only two known cases of binary TNO-Centaurs, (42355) Typhon-Echidna and (65489) Ceto-Phorcys. In the current work we are interested in studying a binary TNO-Centaur that evolves mostly within the planetary region.

We then focused our analysis to the Typhon-Echidna system, since Ceto-Phorcys Ceto has only a small portion of its orbit inside the orbit of Neptune. Through numerical integrations of the N-body gravitational bodies we explored the orbital evolution of 500 clones of Typhon, recording the significant planetary close encounters along its lifetime within the planetary region. Then, we analyzed the effects of those encounters on the binary system. It was found that the vast majority of the extreme close encounters of Typhon-Echidna were performed with the giant planets and that only 22% of those encounters were strong enough to lead to the disruption of the binary. Thus, the Typhon-Echidna system is more likely to cross the planetary region preserving its binarity. We also show cases in which the Typhon-Echidna system reached the terrestrial planets region still as a binary. We estimate a probability of 3.6% of a Typhon-Echidna like system reaching this region. They were detected a few cases of significant close encounters of the binary system with the planets Earth and Venus. There is even a case in which the binary could be disrupted just by those encounters. We discuss how long it took for such event to happen and how long the binary remain here at our neighborhood. It was also explored the past of the system, finding that Typhon must have spent most of its time in the past still as a TNO-Centaur, and that Typhon-Echidna could have survived as a binary for the past 100 Myrs. Overall, it is presented a complete scenario of the possible evolutions for the Typhon-Echidna system showing that a binary system composed of large cometary-type bodies coming from a remote region of the outer Solar System may reach the terrestrial planetary region.