THE dusty disk around the star beta Pictoris is believed to contain a large number of comet-like bodies(1,2). Transient absorption events associated with beta Pictoris have been observed at many wavelengths(3-6) and attributed to cometary objects on eccentric orbits passing between the star and the Earth(7). One unexplained aspect of these events is the large asymmetry between red-shifted and blue-shifted features : similar to 90% of the events are red-shifted(6). We show here that such an asymmetry is a natural consequence of the influence on cometary orbits of secular resonances associated with some planetary systems. Results from numerical integrations of test particles in a model of our Solar System show that the nu(6) secular resonance excites objects initially on near-circular orbits to high eccentricities while aligning their perihelia. Depending on the location of a distant observer, this alignment can produce an asymmetry similar to that observed for beta Pictoris. Our results imply the presence of at least two planets (a prerequisite for the existence of secular resonances) around beta Pictoris.