Study Suggests Icy ‘Centaurs’ Come from Outside Solar System

Researchers have run some apparently very convincing simulations on the likely origins of a group of Centaurs. These are small bodies orbiting around the Sun between our solar system’s outer planets. Those researchers found that they provide evidence of the icy comet-asteroid combos originally arriving in our solar system from interstellar space. They say the speculation is interesting because if these Centaurs were indeed “born” elsewhere, they may one day give us clues as to what kind of physical and chemical differences exist between different solar systems.

An illustration of a Centaur dubbed Chariklo.


A recent study published in the Monthly Notices of the Royal Astronomical Society (via Gizmodo) by Fathi Namouni at the Université Côte d’Azur in France and Helena Morais at São Paulo State University (UNESP) in Brazil supported the research. They based the study on simulations of 17 Centaurs, as well as two trans-Neptunian objects (TNOs). They all display high orbital inclinations relative to the orbital plane of our solar system’s planets. I.e. they orbit around the sun at an angle relative to the major planets in the solar system. You can see this in the clip below.

The researchers took these 19 asteroids—technically Centaurs have both comet and asteroid characteristics, hence their being named after a hybrid horse-human—and ran simulations of where they may have come from in the past. And while many of the simulations resulted in the studied asteroids slamming into the Sun or another planet in our solar system, some of them did show the asteroids eventually settling into a stable orbit around the Sun; the same stable orbit that is verifiable by observation.

Note the white ring closest to top of video marks orbital path of Centaurs.

But those simulations resulting in the asteroids settling into a stable orbit around the Sun all required that the asteroids come from outside our solar system. More specifically, the 19 asteroids almost certainly did not develop alongside the planets and other bodies orbiting the Sun that originally arose from our home star’s accretion disk. This was a disk-shaped cloud of dust and gas left over from the Sun’s formation. (Imagine the disk of dust and gas forming into clumps and eventually into planets and other orbiting bodies thanks to gravity.)

In regards to the significance of the findings, Morais spoke with Science Alert, noting that if the studied asteroids did come from another solar system and if we can one day more closely study the composition of the asteroids, we’ll gain insight into the chemical and physical makeup of other stars that were part of the Sun’s birth cluster. Our star was likely formed alongside roughly 1,000 others from an unthinkably massive nebula.

An illustration of an accretion disk around a protostar (note this is not the Sun).

 Judy Schmidt 

“This population will give us clues about the Sun’s early birth cluster,” Morais told Science Alert, “[as well as] how interstellar asteroid capture occurred, and the role that interstellar matter had in chemically enriching the Solar System and shaping its evolution.”

Featured Image: NASA