1 in 12 Stars May Devour Planets

Stability of Planetary Systems

How Stable Can Planetary Systems Be? Will Earth and its seven siblings continue on their stable celestial orbits forever, or will there come a day when we are randomly expelled from our cosmic home?

Physicists understand the rules governing the orbits of two celestial bodies, but as soon as a third body is added (not to mention a fourth, fifth, or even a hundredth), the dynamics become much more complex. Unpredictable instabilities emerge, where one object may be randomly thrown into space or plummet into its host star.

Space Image

For centuries, scientists have been troubled by the so-called “three-body problem.” One obstacle to understanding it is how little we know about the prevalence of such catastrophically unstable occurrences.

In a new study published in Nature magazine, a research team shed some light on this issue. In their survey of nearby stars, they found that as many as one in twelve stars may have devoured a planet, possibly because the planet created “wobbles” in its orbit and fell into the star.

Studying Twins

Their research revealed that in their sample, at least 8% of star pairs exhibited chemical anomalies, indicating that one star had ingested material from a planet that once orbited it.

To detect this subtle signal, researchers had to rule out other possible explanations for these chemical patterns. They focused on “binary stars,” known to have formed from the same mix of materials at the same time.

This approach helped to eliminate confounding factors, similar to how twin studies are sometimes used in sociology or medical research.

This result stemmed from a twin-star survey named “C3PO,” initiated by co-author Associate Professor Yuan Senting from the Australian National University in the United States, with later involvement from Monash University researcher Liu Fan and others.

Their team collected exquisite spectral data samples from 91 pairs of binary stars – significantly larger than previous similar studies.

They found that some stars differed from their twins, displaying a unique chemical pattern with higher levels of elements like iron, nickel, and titanium compared to other elements such as carbon and oxygen. These differences strongly suggest that the star had consumed a planet.

Unexpected Prevalence of Instability

If a main star devours a member of a planetary system, it indicates that some instability has occurred in that system’s dynamics.

Simulations suggest that such instability may be common in the early life of planetary systems – around the initial one billion years. However, traces of early swallowed planets in stars observed billions of years ago are undetectable.

This indicates that the chemical anomalies we observe are a result of recent instabilities, causing stars to consume some planets or planetary material.

This finding is not entirely unexpected. Theoretical planetary dynamics researchers, including co-author Bertram Bitsch, have noted that many planetary systems are unstable, especially those with a type of planet called “super-Earths,” which are slightly larger than Earth but much smaller than giant planets like Jupiter.

Systems including super-Earths may be particularly unstable. Gravitational tug-of-wars between the main star and its massive planets could lead to instability.

Delicate Balance

This new study prompts scientists to reconsider our position in the universe. While we assume the stability of the solar system as a given, this may not be the norm throughout the universe.

This study does not suggest that we might witness such instability in our solar system. However, even with the new findings, it is important to recognize that planetary consumption and instability still occur in only a minority of cases.

Researchers hope their study inspires more exploration of planetary systems and their relationships with host stars. In fact, our understanding of the dynamics of multi-body systems is still incomplete.

As we continue to unravel the mysteries of the cosmos, such research reminds us of the delicate balance that life on Earth depends on, and the potential fragility of our cosmic home.

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