ARKS: Your solar system was once a wild ride

Astronomers have, for the first time, captured a detailed snapshot of planetary systems in an era long shrouded in mystery. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS), using the Atacama Large Millimeter/submillimeter Array (ALMA), has produced ¹ the sharpest images ever of 24 debris disks, the dusty belts left after planets finish forming.

These disks are the cosmic equivalent of the teenage years for planetary systems—somewhat more mature than newborn, planet-forming disks, but not yet settled into adulthood.

A missing link in planetary family albums

“We’ve often seen the ‘baby pictures’ of planets forming, but until now, the ‘teenage years’ have been a missing link,” says Meredith Hughes, an Associate Professor of Astronomy at Wesleyan University, Middletown, Connecticut, U.S. and co-PI of this study .

“Debris disks are representing the collision-dominated phase of the planet formation process,” explains Thomas Henning, MPIA (Max Planck Institute for Astronomy) scientist and another ARKS co-PI.

“With ALMA, we are able to characterize the disk structures pointing to the presence of planets. In parallel, with direct imaging and radial velocity studies, we are searching for young planets in these systems.”

Our own solar system’s counterpart to this phase is the Kuiper Belt, a ring of icy debris beyond Neptune that preserves a record of massive collisions and planetary migrations from billions of years ago. By studying 24 exoplanetary debris belts, the ARKS team has opened a window into what our solar system went through as the moon was forming and as planets jostled for their final places, and sometimes trading orbits!

Hard to ‘photograph,’ impossible to ignore

Debris disks are faint, hundreds or even thousands of times dimmer than the bright, gas-rich disks where planets are born. The ARKS team overcame these challenges and produced images of these disks in unprecedented detail.

Like teenagers dodging the camera, these faint disks have managed to hide from astronomers for years. But thanks to ALMA, astronomers can now see their complex structures: belts with multiple rings, wide smooth halos, sharp edges, and even unexpected arcs and clumps.

However, ALMA, with its dozens of individual radio telescopes, does not take pictures in the classical sense. Instead, it collects radio signals emitted by dust particles and molecules, which have to be processed and correlated afterwards. Each telescope contributes to the final image, synthesized from the stream of radio waves.

“We’re seeing real diversity—not just simple rings, but multi-ringed belts, halos, and strong asymmetries, revealing a dynamic and violent chapter in planetary histories,” adds Sebastián Marino, program lead for ARKS, and an Associate Professor at the University of Exeter, UK.

Firsts from ARKS

A new benchmark: ARKS is the largest, highest-resolution survey of debris disks, akin to a “DSHARP-for-debris-disks,” setting a new gold standard.

A dynamic, violent youth: About one-third of observed disks show clear substructures (multiple rings or distinct gaps), suggesting legacy features left from earlier, planet-building stages or sculpted by planets over much longer timescales.

Unexpected diversity: While some disks inherit intricate structures from their earlier years, others mellow out and spread into broad belts, similar to how we expect the solar system to have developed.

Clues to planetary “stirring”: Many disks show evidence for zones of calm and chaos, with vertically “puffed-up” regions, akin to our solar system’s own mix of serene classical Kuiper Belt objects and those scattered by Neptune’s long-ago migration.

Surprising gas survivors: Several disks retain gas much longer than expected. In some systems, lingering gas may shape the chemistry of growing planets, or even push dust into wide halos.

Asymmetries and arcs: Many disks are lopsided, with bright arcs or eccentric shapes, hinting at gravitational shoves from unseen planets, leftover birth scars from planetary migration, or interactions between the gas and dust.

Public data release: All ARKS observations and processed data are being made freely available to astronomers worldwide, enabling further discoveries.

Your solar system was once a wild ride

The ARKS results show this teenage phase is a time of transition and turmoil. “These disks record a period when planetary orbits were being scrambled and huge impacts, like the one that forged Earth’s moon, were shaping young solar systems,” says Luca Matrà, a co-PI on the survey, and Associate Professor at Trinity College Dublin, Ireland.

By looking at dozens of disks around stars of different ages and types, ARKS helped decode whether chaotic features are inherited, sculpted by planets, or arise from other cosmic forces. Answering these questions could reveal whether our solar system’s history was unique, or the norm.

Hunting for planetary architects

The ARKS survey’s findings are a treasure trove for astronomers hunting for young planets and seeking to understand how planet families, like our own, are built and rearranged.

“This project gives us a new lens for interpreting the craters on the moon, the dynamics of the Kuiper Belt, and the growth of planets big and small. It’s like adding the missing pages to the solar system’s family album,” adds Hughes.