3.7 Billion Miles Away: Hubble Uncovers a Hidden Trio That Could Rewrite Kuiper Belt History

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3.7 Billion Miles Away: Hubble Uncovers a Hidden Trio That Could Rewrite Kuiper Belt History

A Rare Trio in the Kuiper Belt?

If confirmed, the 148780 Altjira system would be only the second known three-body system in this distant region of space, suggesting that many more could exist. This discovery could support a key theory about the early history of our solar system and how Kuiper Belt Objects (KBOs) originally formed.

“The universe is filled with different kinds of three-body systems, including the closest stars to Earth, such as the Alpha Centauri star system. Now, we’re starting to see that the Kuiper Belt might not be an exception,” said lead researcher Maia Nelsen, a physics and astronomy graduate from Brigham Young University in Provo, Utah.

Kuiper Belt Objects: Relics of the Early Solar System

First discovered in 1992, KBOs are ancient, icy remnants from the birth of our solar system, located beyond Neptune’s orbit. Over 3,000 of these objects have been cataloged so far, but scientists estimate that there may be hundreds of thousands more, each spanning over 10 miles in size. The largest known KBO is the dwarf planet Pluto.

Hubble’s latest finding is a crucial piece of evidence supporting a theory that KBOs may have formed differently than previously thought. Instead of forming through violent collisions in a crowded Kuiper Belt, some of these three-body systems may have taken shape directly from the gravitational collapse of material surrounding the young Sun, about 4.5 billion years ago. It’s well known that stars often form in pairs or trios through gravitational collapse, but the idea that objects in the Kuiper Belt could form the same way is still being investigated.

Altjira: A Hidden Trio in the Outer Solar System

The Altjira system lies in the farthest reaches of our solar system, about 3.7 billion miles away—44 times the distance between Earth and the Sun. Hubble’s images reveal two visible KBOs orbiting about 4,700 miles (7,600 kilometers) apart. However, scientists analyzing the movement of these objects believe that one of them is actually a closely bound pair of bodies that are too near to each other to be distinguished at this great distance.

A Growing Population of Three-Body Systems?

Currently, about 40 binary objects have been identified in the Kuiper Belt. Now, with a second potential three-body system, researchers believe they may not be looking at a rare outlier but rather a hidden population of triple systems that formed under the same conditions. However, proving this requires time and repeated observations.

The only KBOs studied in detail so far are Pluto and Arrokoth, which NASA’s New Horizons mission visited in 2015 and 2019. New Horizons revealed that Arrokoth is a “contact binary”—two objects that slowly moved closer together over time until they touched or merged, often forming a peanut-like shape. Researcher Darin Ragozzine describes Altjira as a “cousin” of Arrokoth, part of the same class of Kuiper Belt objects. However, Altjira is estimated to be ten times larger than Arrokoth, measuring about 124 miles (200 kilometers) across.

An Eclipsing Event Offers New Clues

While no mission is currently planned to visit Altjira for a close-up study like Arrokoth, Nelsen pointed out that an upcoming celestial event could provide a rare opportunity to learn more about this mysterious system.