Alpha Centauri may have a super Jupiter in orbit

The three-body problem represents one of the most complex challenges in physics. The gravitational interactions and resulting motions between three massive bodies are notoriously difficult to predict due to their inherent instability. A classic example is that of a planet orbiting two stars, also known as the “restricted three-body problem.” Despite this complexity, there are potentially stable orbit configurations for a planet in such systems. New research suggests that the nearby star system Alpha Centauri AB may harbor a Super Jupiter in stable orbit.

Understanding the Three-Body Problem

THE three body problem is one of the most fascinating and complex puzzles in physics and astronomy. At its core, it explores the gravitational interactions between three large masses, such as stars or planets, and the unpredictable challenges they present. Imagine three massive objects moving through space, each attracted by the gravity of the others. The dynamics of this system are extraordinarily complex, because each body exerts an attractive force on the other two simultaneously. This configuration makes the individual trajectories of the bodies difficult to predict in the long term. One of the most intriguing examples of the three-body problem is that of a planet orbiting two starsas found in binary stellar systems. This scenario is often called the “restricted three-body problem.” Unlike a simple orbit around a single star, where Kepler’s laws allow for relatively accurate predictions, a planet in a binary system must navigate between two major gravitational influences. This challenge is exacerbated by the inherent instability of these configurations. Orbits can be chaotic and sensitive to small perturbations, meaning that small initial variations can lead to completely different outcomes over cosmic timescales.

The Alpha Centauri case

However, in the case of a pair of stars like Alpha Centauri ABwhere the two components (Alpha Centauri A and Alpha Centauri B) are relatively far from each other (about 4.37 light years) compared to a third object, it is possible to envisage potentially stable orbits for smaller bodies like planets. As a reminder, Alpha Centauri AB is made up of two stars similar to the Sun, Alpha Centauri A and Alpha Centauri B. Alpha Centauri A is a G-class star slightly more massive than our Sun, while Alpha Centauri B is a K-class star slightly less massive. In the context of recent worksso researchers studied our nearest binary neighbor to understand whether the system could accommodate a “super Jupiter” and determine what orbit this giant planet could follow.

Size comparisons for Alpha Centauri A and B (the closest pair to Earth), Proxima Centauri (the closest individual star), and the Sun. Credits: Planetary Habitability Lab/UPR Arecibo

Comparison with other binary systems and implications for stability

For this study, the researchers compared this system with another binary system known as GJ65AB (Gliese 65). Although GJ65AB is composed of two more massive stars, the similarities in their mass ratios and orbital eccentricities make the comparison relevant. Furthermore, GJ65AB hosts a Neptune-mass exoplanet in a stable orbit, suggesting that similar conditions might be favorable for Alpha Centauri AB. To do this, the researchers used the method of average exponential growth factor of close orbits (MEGNO). This is a technique used to assess the stability of planetary orbits by measuring the exponential growth of orbital deviations. Specifically, the team ran simulations to determine the orbital parameters that could allow a Jupiter-mass planet to maintain a stable orbit around Alpha Centauri A or B. The results then indicated a potential stability zone for a planet with an approximate mass of 350 times that of Earthwith specific orbital parameters. Note that although his simulations show the possibility of a stable orbit for a Super Jupiter in Alpha Centauri AB, this does not guarantee the actual existence of such a planet.