THE PHOTOMETRIC-METHOD OF EXTRASOLAR PLANET DETECTION REVISITED

We investigate the geometry concerning the photometric method of extra solar planet detection, i.e., the detection of dimunition of a parent star's brightness during a planetary transit. Under the assumption tha t planetary orbital inclinations can be defined by a Gaussian with a s igma of 10-degrees centered on the parent star's equatorial plane, Mon te Carlo simulations suggest that for a given star observed at an incl ination of exactly 90-degrees, the probability of at least one Earth-s ized or larger planet being suitably placed for transits is approximat ely 4%. This probability drops to 3% for a star observed at an inclina tion of 80-degrees, and is still approximately 0.5% for a star observe d at an inclination of 60'. If one can select 100 stars with a pre-det ermined inclination > 800, the probability of at least one planet bein g suitably configured for transits is 95%. The majority of transit eve nts are due to planets in small-a orbits similar to the Earth and Venu s; thus, the photometric method in principle is the method best suited for the detection of Earthlike planets. The photometric method also a llows for testing whether or not planets can exist within binary syste ms. This can be done by selecting binary systems observed at high orbi tal inclinations, both eclipsing binaries and wider visual binaries. F or a ''real-world'' example, we look at the alpha Centauri system (i = 79.2-degrees). If we assume that the equatorial planes of both compon ents coincide with the system's orbital plane, Monte Carlo simulations suggest that the probability of at least one planet (of either compon ent) being suitably configured for transits is approximately 8%. In co nclusion, we present a non-exhaustive list of solar-type stars, both s ingle and within binary systems, which exhibit a high equatorial incli nation. These objects may be considered as preliminary candidates for planetary searches via the photometric method.