Last year, researchers hypothesized that some icy objects in the outer solar system travel into the inner solar system thanks to a special gateway located beyond the orbit of Jupiter. Now the team are watching this action take place.
Between the orbit of Jupiter and Neptune, there is a population of objects known as Centaurs that are on an unstable orbit and have an expected lifetime of a few million years. A possible future for these objects is to leave the Centaur population and become a member of the Jupiter Family of Comets (JFC), which are a group of objects orbiting the Sun in less than 20 years.
As reported in The Astrophysical Journal Letters, Comet P/2019 LD2 (ATLAS) appears to be right in that transition state. It is currently near the gateway and becoming more active. The team thinks it will become a fully-established member of the JFC in the next 40 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. The dynamical gateway is a region beyond Jupiter, extending to just inside of Saturn’s influence,” lead author Dr Jordan Steckloff, from the Planetary Science Institute, said in a statement. “The newly discovered comet 2019 LD2 (ATLAS) is a Centaur, but is actively transitioning into a JFC. It is in the very earliest parts of this transition, and is the first time an object has been discovered prior to embarking on this transition.”
The concept of the comet gateway was put forward to explain the number of short-period comets that exist in the solar system. The heat of the Sun should destroy them but, given their numbers, researchers think the population is regularly re-supplied with new recruits.
The scenario is as follows: an icy body from beyond the orbit of Neptune eventually comes close enough to the blue giant planet to push the comet inward to the Centaur population, trapped between the four giant planets. Their gravity makes the comet's orbit unstable and, over time, it moves inward to the comet gateway where it transitions to a JFC.
“Crucial to understanding how these categories of objects came about is understanding the processes that they experience, and how they have evolved over time to become the objects that we see today,” Steckloff said. “LD2 represents a unique opportunity to investigate the connection between the JFC and Centaur boxes; to understand how they are different and how they are similar. It presents us with a chance, during our lifetime, to understand how a Centaur physically transforms into a JFC, rather than just dynamically.”
Studying LD2 over the next 40 years will provide invaluable insight into the formation of the JFC and how short-period comets form.
