1 in 12 Stars May Devour Planets

Stability of Planetary Systems

How stable can a planetary system be? Will Earth and its seven siblings continue to orbit steadily in their celestial paths forever, or will there come a day when we are randomly ejected from our cosmic home?

Physicists understand the rules that govern the orbits of two celestial bodies, but once a third body is introduced (not to mention a fourth, fifth, or a hundredth), dynamics become much more complex. Unpredictable instabilities arise, where one object may be randomly flung into space or plunge into its host star.

Stars devouring planets

For centuries, scientists have been troubled by the so-called “three-body problem.” One obstacle to understanding it is our limited knowledge of how common such catastrophic instabilities are.

In a new study published in the journal Nature, a research team sheds 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 caused “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, suggesting that one of the stars had consumed material from a planet that once orbited it.

To detect these subtle signals, researchers had to rule out other possible explanations for these chemical patterns. They focused on “binary stars,” known to have been born from the same material mix at the same time.

This method helps eliminate confounding factors, similar to how studies on twins are sometimes utilized in sociology or medical research.

These findings stem from a double-star survey named “C3PO,” initiated by co-author Dr. Sen Ting Yuan from the Australian National University in the United States, later joined by Dr. Fan Liu from the School of Physics and Astronomy at Monash University and others.

Their team collected detailed spectral data samples from 91 pairs of binary stars — a significant increase from similar studies conducted in the past.

They identified some stars that differed from their twin counterparts, showing a distinctive chemical pattern with higher levels of elements such as iron, nickel, and titanium compared to other elements like carbon and oxygen. These differences strongly indicate that the star had consumed a planet.

Unpredictability Might Be More Common Than Expected

If a primary star devours one or more members of a planetary system, it indicates that some instability has occurred in that system’s dynamics.

Simulations suggest that this kind of instability might be quite common in the early life of a planetary system — around the initial one billion years. However, traces of early swallowed planets in stars observed billions of years ago are undetectable.

This implies that the chemical anomalies we see are caused by recent instabilities, leading to stars consuming some planets or planetary material.

This finding is not entirely surprising. Theoretical planetary dynamics researchers, including their co-author Bertram Bitsch, have noticed that many planetary systems are unstable, especially those with planets known as “super-Earths,” which are slightly larger than Earth but much smaller than gas giants like Jupiter.

Systems including super-Earth planets could be particularly unstable. Gravitational tug-of-war between the primary star and its high-mass planets could lead to instability.

Delicate Balance

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

Although this study does not suggest we might see such instability in our solar system, it is essential to acknowledge that planetary consumption and instability still occur in only a minority of cases.

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

As we continue to unravel the mysteries of the universe, such research serves as a reminder of the delicate balance that life on Earth depends on and the potential vulnerability of our cosmic home.

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