The transport of large near-Earth objects into the Centaur region

Context . Near-Earth objects (NEOs) and Centaurs are minor bodies that orbit the Sun in the terrestrial and giant-planet regions, respectively. Recent studies show that approximately 9% of the known large NEOs that leave the terrestrial planet region are transported to the Centaur region, where they can remain for at least 5000 years. Aims . We present a detailed analysis of the transport of NEOs to the Centaur region. We refer to these objects as NEO-Centaurs. Methods . We analyzed numerical integrations of the N -body gravitational problem, including the Sun, the eight planets, and a sample of 839 known NEOs larger than 1 km (absolute magnitude H < 18). We also conducted a statistical analysis based on 8390 clones to quantify the likelihood of NEO transport to the Centaur region. Results . A significant fraction of NEOs is likely transported to the Centaur region over an average timescale of approximately 7.8 Myr. The median residence time in the Centaur region is estimated to be 20 000 years. The average residence time is 2.3 Myr. We also identify one case in which the NEO-Centaur reached the trans-Neptunian objects (TNOs) region. The statistical analysis confirms a significant likelihood that NEOs are transported to the Centaur region. The probabilistic measure based on clone statistics indicates that only 13% of NEOs larger than 1 km have no successful clones reaching the Centaur region, while 14% have a probability greater than or equal to 50% of becoming NEO-Centaurs. Conclusions . We infer that NEO-Centaurs comprise 0.01-1% of the population of Centaurs larger than 1 km and are likely composed of bodies smaller than 5 km in diameter.