Friday , September 24 2021

How are planets formed in binary systems?

The formation of planets is believed to occur in the protoplanetary disk. The most widely accepted mechanism for how planets form is nuclear deposition. Nuclear accumulation develops from the collision and coagulation of solid particles into increasingly larger bodies until a sufficiently large planetary embryo is formed.

However, this theory is valid for planetary systems that form around a single star, but planet formation is more complex in binary stars.

Many exoplanets have been observed in binary systems. Now the real question is how did they get here. Some astronomers have even suggested that these planets glide through interstellar space and are absorbed by the gravity of a binary system, for example.

To solve the mystery of how planets form in a binary system, scientists from the University of Cambridge and the Max Planck Institute for Extraterrestrial Physics have developed the most realistic model to date of planet formation in binary star systems. Their models showed that exoplanets in binary star systems exist without annihilation in chaotic natal environments.

The model uses realistic physical inputs and takes into account processes that are often overlooked, such as the gravitational effect on the motion of planetesimals inside the gas disk.

Scientists have studied a kind of binary system – our nearest neighbor Alpha Centauri. The model shows that Alpha Centauri makes the planets start at least 10 kilometers in diameter and the protoplanetary disk itself is close to circular without significant irregularities.

from the Department of Applied Mathematics and Theoretical Physics, Cambridge. Roman Rafikov said: “The disk is known to act as a kind of wind, directly affecting planets through gas entrainment. A few years ago, we noticed that, in addition to gas entrainment, the disk’s gravity itself dramatically alters the planetary dynamics, in some cases allowing planets to form despite gravitational perturbations from stellar companions.

“The model we built combines this work and other previous work to test theories of planet formation.”

Journal Reference:
  1. Kedron Silsbee and Roman R. Rafikov. ‘Planet Formation in Stellar Binaries: Global Simulations of Planetary Growth.’ Astronomy and Astrophysics (2021). DOI: 10.1051/0004-6361/20214113

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