NASA's Hubble Finds Kuiper Belt Duo May Be Trio

March 04, 2025 11:00AM (EST)Release ID: 2025-007
Illustration of two large, cratered rocks in the foreground right. Another rock is seen in the distance to the left. The black background of space shows the hazy Sun and zodiacal light due to dust in the solar system, as well as scattered distant stars. The words "Artist's Concept" appear in gray at the bottom left.

Summary

A potential triple system of Kuiper Belt objects, only the second ever found, would support the theory that these rocky bodies form by gravitational collapse, like stars.

The universe contains a range of gravitationally bound three-body systems, from triple star systems to planets with two moons, like Mars. New research suggests that objects in the solar system's Kuiper Belt may also be in the triple club, as a second system, already identified as a binary, shows signs of containing a third member that is so close to its companion it can only be identified by observing the system's orbital dynamics. Confirming two triple systems in the Kuiper Belt would raise the likelihood that there are many other hidden triples there waiting to be recognized. The larger implication of this research is its support for a formation theory for Kuiper Belt objects known as the streaming instability hypothesis, which proposes that they formed not by collisions, but originated as triple systems through gravitational collapse.

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