Small Icy Bodies Travel Within a Gateway Region of Space and Turn into Comets

Small Icy Bodies Travel Within a Gateway Region of Space and Turn into Comets

Starting as small, icy bodies on the outskirts of the solar system, comets turn into spectacular streaks of light after they pass by a “gateway” close to Jupiter, based on new analysis.

This gateway is an area of space where objects known as centaurs small, icy bodies that orbit between Jupiter and Neptune begin to push closer to the sun. As they do, they heat up and turn into “active,” primarily releasing a dusty halo of gas which makes these small bodies, technically, comets. “We realized there is a nexus point in orbital space where small bodies change their orbit that we nicknamed ‘the gateway,'” stated lead author Gal Sarid, a planetary scientist at the University of Central Florida.

The gateway region is a donut that wraps across the inner solar system, containing many possible orbits within its thick ring. Sarid and his team first came up with the gateway concept after taking a look at a peculiar centaur named 29P/Schwassmann-Wachmann 1 or SWI. Although technically a centaur, SWI is very active, frequently releasing gases as a comet does, Sarid stated.

The researchers then modeled other such small, icy bodies in the outskirts of the solar system, and located that lots of them took the same path that SWI did originate beyond Neptune, moving into an unpredictable orbit between Jupiter and Neptune, and then to this gateway region. The scientists discovered that one in five centaurs that they analyzed entered the same orbit as SW1 at one point in time.

Making this is a similar journey, centaurs give rise to most of the Jupiter family comets, a group of comets known as “short-period comets,” which means those that orbit around the sun in less than 200 years. Their models indicate that centaurs do not remain in the gateway region for long; most turn into Jupiter family comets within a few thousand years and move into the inner solar system. That is a short time, considering that comets can live for millions or billions of years.

However, this is not a one-way journey. The researchers’ models show that Jupiter family comets also generally move back into the gateway region, trekking away from the sun. The information showed that 70% of Jupiter family comets spend time in the gateway region, both moving in toward the inner solar system or moving out to the outskirts. “They will go back and forth like a revolving door,” Sarid stated.