Centaur Longevity Revisited: Lifetime Dispersion and the Bailey & Malhotra Classifications under Modern Orbital Solutions

RESUMO

Centaurs occupy dynamically unstable orbits between Jupiter and Neptune and are typically removed by giant-planet encounters within a few Myr. Bailey and Malhotra (hereafter BM09) classified the known Centaurs, from 2007 orbits, into a short-lived diffusing class (D), a resonance-hopping class (R), and a long-lived, quasi-stable class (Q); their sole Q object, 2005 TH173, was fit to a 17\,d arc. We revisit both halves of that analysis on modern Jet Propulsion Laboratory Small-Body Database (SBDB) orbits (retrieved 2026-07-26), integrating clone ensembles of each object with the REBOUND WHFast $N$-body integrator. We ask (i) whether tighter orbital precision narrows the dispersion in clone lifetimes, and (ii) whether the BM09 labels survive on updated elements. Among 65 genuine Centaurs with arc $\ge 30$\,d and no censored clones, $\sigma(\log_{10}\mathrm{lifetime})=0.54$\,dex (a factor of 3.5). Conditioned on present-day $a$, $e$, $i$, and $q$, this dispersion is insensitive to relative semimajor-axis uncertainty (slope $=-0.002$\,dex per decade in $\sigma_a/a$; 95\% confidence interval $-0.034$ to $+0.030$) --- a chaos floor. On the D/Q axis, 49/50 comparable objects retain their BM09 class; 2005 TH173 is the exception (Q$\to$D): 80/100 clones escape before 10\,Myr (median 2.99\,Myr), and a 40\,Myr integration of the same initial conditions returns 88\,D / 12\,R / 0\,Q. None of the 30 multi-opposition 2007 orbits changes class; two short-arc objects leave the Centaur zone.}