  The recently discovered object P/2019 LD2 (ATLAS) was initially thought to be
a Jupiter Trojan asteroid, until dynamical studies and the appearance of
persistent cometary activity revealed that this object is actually an active
Centaur. However, the dynamical history, thermal environment, and impact of
such environments on the activity of 2019 LD2 are poorly understood. Here we
conduct dynamical simulations to constrain its orbital history and resulting
thermal environment over the past 3000 years. We find that 2019 LD2 is
currently in the vicinity of a dynamical "Gateway" that facilitates the
majority of transitions from the Centaur population into the Jupiter Family of
Comets (JFC population; Sarid et al. 2019). Our calculations show that it is
unlikely to have spent significant amounts of time in the inner solar system,
suggesting that its nucleus is relatively pristine in terms of physical,
chemical, and thermal processing through its history. This could explain its
relatively high level of distant activity as a recently activated primordial
body. Finally, we find that the median frequency of transition from the Gateway
population into the JFC population varies from once every ~3 years to less than
once every 70 years, if 2019 LD2's nucleus is ~1 km in radius or greater than 3
km in radius. Forward modeling of 2019 LD2 shows that it will transition into
the JFC population in 2063, representing the first known opportunity to observe
the evolution of an active Centaur nucleus as it experiences this
population-defining transition.
