Dynamics of Planets Orbiting in the Alpha Centauri AB Stellar System

The alpha Centauri system contains the Solar System’s closest stellar 
neighbors.If an earthlike planet is present in the system, it could 
in principle be detected using a small space-based telescope.As alpha 
Centauri is billions of years old, planets are only expected to be 
found in regions where their orbits are long-lived.We evaluate the 
extent of the regions within the alpha Centauri AB system where 
small planets are able to orbit for billion-year timescales, as well 
as how closely-spaced planetary orbits can be within those regions 
in which individual planets can survive.Individual planets on nearly 
circular, coplanar orbits can survive throughout the habitable zones 
of both stars.However, perturbations from the companion star imply 
that the spacing of such planets in multi-planet systems must be 
significantly larger than the spacing of similar systems orbiting 
single stars in order to be long-lived. Because the binary companion 
induces a forced eccentricity upon the orbits of planets in orbit 
around either star, appropriately-phased circumstellar orbits with 
small initial eccentricities are stable to slightly larger initial 
semimajor axes than are initially circular orbits.Small initial 
eccentricities have a much larger affect on how closely planetary 
orbits can be spaced.Our results are of special interest as they can 
guide observers designing instrumentation and search strategies to 
attempt to discover planets orbiting the nearest sunlike stars.remains 
significantly higher than for planets orbiting single stars.