'Streaming instability' hypothesis: What is it and how is Hubble involved?

The Kuiper belt, a distant region of icy bodies beyond Neptune, is home to many celestial wonders. Among them, one particular trio of space rocks has recently caught the attention of scientists.

Cosmic systems involving three orbiting bodies have always challenged astronomers as it is difficult to predict the paths of the three gravitationally bound objects.

Interactions between the gravitational fields of the three bodies tend to lead to chaotic dynamics, which has given rise to the “three-body problem.”

The discovery that a previously identified binary system in the Kuiper belt may actually involve three bodies could reshape our understanding of how objects in the Kuiper belt form and evolve.

The research team that have identified the system claim to have found a stable group of three bodies, which is highly unusual but not entirely unheard of. This would marking a significant breakthrough in planetary science.

What astronomers found

Researchers from the Brigham Young University in Provo, Utah, believe they’ve uncovered the second trio of space rocks ever identified in the Kuiper belt.

If verified, this suggest that there may be other three body systems present. It adds credence to a unique theory on the history of our solar system and the formation of Kuiper belt objects (KBOs).

“The universe is filled with a range of three-body systems, including the closest stars to Earth, the Alpha Centauri star system, and we’re finding that the Kuiper belt may be no exception,” says the study’s lead author, Maia Nelsen, a physics and astronomy graduate of BYU.

What are Kuiper Belt objects?

Catalogued in 1992, KBOs are primordial icy remains from the very beginnings of our solar system. The belt where these objects are found lies well beyond Neptune’s orbit.

To date, scientists have recorded over 3,000 KBOs and predict a possible number in the hundreds of thousands if they include those bigger than 10 miles (16 kilometers) in diameter.

Dwarf planet Pluto ranks as the biggest KBO.

Formation of Kuiper belt objects

The new Hubble breakthrough offers key insights into a KBO formation theory in which the three small, rocky bodies would not have formed as the result of collision in the busy Kuiper belt, but rather from the gravitational collapse of matter in the disk of material surrounding the newly formed Sun.

This likely happened around 4.5 billion years ago.

By comparison, stars are known to form by the gravitational collapse of gas, often in pairs or triples.

The notion that celestial bodies in the Kuiper belt form similarly is a fascinating concept that is currently under review.

Insights into the Altjira system

Located in the outer realms of our solar system, some 44 times the distance between Earth and the Sun, the Altjira System is the subject of this compelling research.

Though two KBOs were seen in Hubble images of this system, scientists now believe the inner object is, in fact, a pair of bodies that appears as one due to their close proximity and their great distance from observers on Earth.

The scientists explain that differentiating the two tiny bodies at such a great distance requires non-imaging methods.

The team monitored the Altjira system over a 17-year period, observing the unique co-orbital movement of the outer object. Over time, they noticed subtle shift in orbit that was not expected.

Multiple hypotheses for the Altjira system

In analyzing the Hubble footage, the team found that the strongest evidence supported the idea of a triple system.

They also considered that the inner object could be a contact binary (two separate bodies so close that they touch each other) or an irregularly flat object reminiscent of a pancake.

Currently, the researchers estimate there are around 40 binary objects in the Kuiper belt.

With the discovery of a potential second triple system, it is possible that these systems are not single eccentricities but rather examples of an entire population of three-body systems formed under similar conditions.

Historically, the only KBOs studied in detail are Pluto and the smaller object Arrokoth, which were explored by NASA’s New Horizons missions in 2015 and 2019, respectively.

Arrokoth is a contact binary, a pair of objects that have moved ever closer to each other and assumed a peanut shape.

What happens next?

The team describes Altjira as a close relative of Arrokoth, as it hails from the same Kuiper belt group.

They estimate Altjira to be approximately ten times larger though, with a diameter of 124 miles (200 kilometers).

Even though there’s no planned mission to see Altjira as closely as Arrokoth was observed, the researchers gleefully await an upcoming opportunity for further study.

Over the next decade, they will get the chance to observe the outer body passing in front of the central body, which will give them a chance to learn more about this intriguing system and other aspects of the universe

In addition, NASA’s James Webb Space Telescope will join the study in its upcoming Cycle 3 observations, and it will add new evidence about these three frosted cosmic bodies.

The study was published in The Planetary Science Journal.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–