Each star's neighborhood affects the type of planets that form

Stars have long inspired curiosity among observers, but our understanding of their birth and the creation of planets around them is still evolving. New insights from recent research suggest the story of how planetary systems come together is more dynamic than previously believed.

Paolo Padoan, an ICREA research professor at the Institute of Cosmos Sciences of the University of Barcelona (UB) and currently on leave at Dartmouth College, has helped highlight an alternative angle on these processes.

Padoan’s findings center on the role of Bondi-Hoyle accretion, a mechanism that appears to add crucial mass and momentum to young stellar disks.

Stars gather gas from their surroundings

Early ideas suggested that protoplanetary disks only shrink as they funnel material onto their stars. Observers assumed these disks were finite reservoirs that gradually dissipated, but new results call for a broader interpretation.

“Stars are born in groups or clusters within large gas clouds and can remain in this environment for several million years after their birth,” said Padoan. His perspective suggests that stars do not develop in isolation, which is a key detail for understanding disk evolution.

Researchers have also noted how local conditions can vary from one star cluster to another. These variations might explain why planetary systems display such a wide range of orbits and compositions.

Star clusters shape planet birth

Stars interact with surrounding gas that continues to feed the disk, even after the initial collapse. This constant influx extends the lifetime of disks and boosts the raw material available for planet formation.

Many star clusters form in immense clouds of volatile gas, which move at high speeds. That movement, often described as supersonic turbulence, can give each cluster a distinct profile of density, temperature, and motion.

Scientists studying these environments see large-scale flows that transport matter across vast distances measured in trillions of miles. These flows may bring in new elements or compounds that alter how planets eventually take shape.

Disks grow larger over time

“After a star forms, its gravity can capture more material from the parental gas cloud… but enough to restructure its disk,” said Padoan. This process ensures disks may grow larger over time, contradicting classic views that they only lose mass.

By tracking the motion of interstellar gas, scientists observed how random density changes produce significant spins in these disks. That insight opened the door to a theory that better fits actual observations.

The disk’s size can influence the distribution of dust grains and ice, which are key ingredients for planet cores. If the disk extends farther, planets can form at greater distances from the star, broadening the possibilities for planetary orbits.

How gas shapes stars and planets

Teams employed advanced modeling to simulate the swirl of gas around early-stage stars. This allowed them to test various conditions and see which setups matched data collected by ALMA.

“Comparing the observable data from the simulations with real observations is crucial to validate the simulations,” said Veli-Matti Pelkonen, an ICUCB researcher and team member who underscores the value of these methods.

The researchers used simulation outputs to track complex properties that remain invisible in real-life images.

Their computational approach included the influence of magnetic fields, which can change the way gas flows inside stellar nurseries. The experts also accounted for chaotic velocities that shift direction rapidly.

More gas means more planets

The researchers believe that the extra mass provided by Bondi-Hoyle accretion supports the creation of more robust disks. A stronger disk may hold onto the gas and dust needed to form multiple generations of planetary cores.

The added spin from the environment can influence how material circulates before it clumps into planetary bodies. This dynamic flow could also guide the formation of planetary atmospheres, which is critical for any potential habitability.

In some cases, the strong influx of gas might even reshape the arrangement of emerging planets. That reshaping has potential implications for both planet sizes and orbital separations.

Broader implications for exoplanets

Many newly discovered exoplanets have masses and orbits that differ from our solar system. If disks can capture extra material from their surroundings, it might explain these unexpected configurations in other star systems.

Studies of distant clusters have yielded surprising results about how often planet-hosting stars appear in tight groups. Researchers continue to gather evidence on whether these conditions correlate with diverse planetary architectures.

Because environment shapes disk properties, the search for life-supporting planets might hinge on understanding local cloud conditions. More data from exoplanet surveys could link these conditions to signs of potential water or other life-essential molecules.

Predicting star and planet formation

“With the increase of the computing power of supercomputers, these advances will continue to increase our understanding of star formation,” said Pelkonen.

Astronomers are already pairing these high-resolution simulations with data from advanced telescopes like the James Webb Space Telescope, aiming for better clarity on disk structures.

Expanding knowledge of disk behavior offers a fresh path to interpreting how planets develop in diverse environments. By mapping these steps, researchers hope to refine our understanding of where life-friendly planets might arise in the cosmos.

Observing how gas moves in stellar nurseries may lead to refined models that predict how many Earth-like worlds could form. That level of insight would be a turning point for anyone exploring the probability of life beyond our neighborhood.

The study is published in Nature Astronomy.

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