Repeated spectroscopic observations of beta Pictoris have been perform
ed since 1985 and revealed the presence, in many metallic lines like C
a II, Mg II, Fe II, ..., of strong sporadic circumstellar absorption,
redshifted by tens to hundreds of km s-1 with respect to the star and
highly time-variable (time-scales of days or hours). We have tentative
ly interpreted these variable events as the spectral signature of infa
lling cometary-like bodies, when evaporating in the vicinity of the st
ar. This scenario has been furthermore theoretically studied, and we s
howed that it could indeed explain correctly the observations with the
ir peculiar characteristics, like (1) the behavior difference between
visible and UV lines, (2) the unusual line ratios, (3) the surprising
presence of Al III absorption lines. Constraints deduced from both obs
ervational data and theoretical study allowed us to suggest that a pla
net within the disk could be responsible, by perturbations, of this hi
gh rate infall of small bodies towards the star (> 100 per year).