  The structure of the Borromean nucleus $^9$Be ($\alpha+\alpha+n$) is
addressed within a three-body approach using the analytical transformed
harmonic oscillator method. The three-body formalism provides an accurate
description of the radiative capture reaction rate for the entire temperature
range relevant in Astrophysics. At high temperatures, results match the
calculations based on two-step sequential processes. At low temperatures, where
the particles have no access to intermediate two-body resonances, the
three-body direct capture leads to reaction rates larger than the sequential
processes. These results support the reliability of the method for systems with
several charged particles.
