A recent plan would send a Centaur mission to Jupiter’s orbit and follow a comet through formation.

From Mercury to the depths of the distant Kuiper Belt, there aren’t many unexplored corners of the solar system out there. One class of object, however, remains to be visited: the transitional Centaurs out beyond the orbit of Jupiter. Now, a new study out from the the University of Chicago recently accepted in The Planetary Science Journal looks at the feasibility of sending a mission by mid-century to intercept, follow and watch a Centaur asteroid as it evolves into a mature inner solar system comet.

It’s a major mystery for planetary astronomy: how do comets get trapped in short-period path (that is, a comet with an orbital period of less than 200 years) in the inner solar system? Jupiter plays a major role in this regard, deflecting incoming debris both into and out of the solar system. On approach, a prospective new comet to the inner solar system stands a 40% chance of having its orbit altered by Jupiter. A prime example was long-period comet Hale-Bopp, which had its orbit shortened from 4,200 to 2,533 years during its 1997 perihelion passage. And as recently witnessed (twice!) in the past month, Jupiter also gets frequently smacked by incoming asteroids and comets.

Indeed, a close passage near Jupiter is a gateway into—as well as a ticket out of—the solar system.

The distribution of known Centaurs though the outer solar system. Credit: Eurocommuter/Wikimedia Commons Creative Commons 3.0-share alike license.

Why Centaurs

2060 Chiron was first Centaur asteroid discovered and recognized as such in 1977, followed by 5145 Pholus in 1992. Today, 452 Centaurs are known of, ranging from the orbit of Jupiter to Neptune. Clearly, these are intriguing transitional objects in their own right, and worthy of study not only as pristine samples of the early primordial solar system, but also as transitional objects between inert icy asteroids and active comets. To get an idea of just how strange Centaurs are, witness the bizarre world of 10199 Chariklo, the only asteroid known to possess a ring system. With orbits crossing those of the main larger planets of the solar system, an object has an average lifespan as a Centaur of only a few million years, which is short, as the multi-billion year history of the solar system goes. And though we haven’t visited a Centaur yet per se, we may have gotten a preview of one of these strange objects during flybys of the outer moons of Saturn, and the ice giant worlds of Uranus and Neptune during the Voyager 2 mission.

The population of known Centaurs and the distribution in the outer solar system, showing the transition regions and the ‘dynamical gateway’ were Centaurs become Jupiter-family comets. Credit: University of Chicago/D. Seligman. Used with permission.

“Centaurs are extremely interesting for many reasons,” lead researcher on the study Darryl Seligman (University of Chicago Department of Geophysical Sciences) told Universe Today. “I think the most intriguing aspects of this population is that they will show us the missing link in our understanding of the temporal evolution of the minor bodies in the Solar System. The Centaurs in between the giant planets serve as the source population for the Jupiter family comets, which presumably originate out past Neptune.”

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