A new study alters our understanding of how comets arrive form the outer limits of the solar system and are funnelled into the inner solar system. A so called orbital 'gateway' is proposed through which comets pass through before they approach the Sun. The gateway was uncovered by simulating centaurs, the small icy bodies travelling on chaotic orbits between Jupiter and Neptune. When icy bodies such as centaurs and comets approach the Sun they begin to release dust and gases and sport extensive tails. See https://phys.org/news/2019-09-comet-gateway-solar-fundamental-evolution….
The original purpose of the research was to shed some light on the behaviour of one centaur in particular, SW1. It is highly active and there are frequent explosive outbursts that occur at a distance far away from the Sun. This is inexplicable they say. SW1 has been categorised as an object in between centaurs (or the more docile of them) and Jupiter Family comets. So, they decided to look at centaurs as a whole and not just SW1 and found they were inclined to enter an orbit similar to SW! at some point in their lifetime. It seems SW! is a centaur caught in the act of dynamically evolving into a Jupiter Family comet. Not only that but centaurs passing through the gateway are the source of more than two thirds of such comets, In other words, SW1 will at some point become a comet and enter the inner solar system, an amazing verification of Napier's recent papers. Se https://arxiv.org/pdf/1908.04185.pdf