 There was a good deal of interest in the 2004 transit as scientists attempted to measure the pattern of light dimming as Venus blocked out some of the Sun 's light , in order to refine techniques that they hope to use in searching for extrasolar planets . Current methods of looking for planets orbiting other stars only work for a few cases : planets that are very large ( Jupiter @-@ like , not Earth @-@ like ) , whose gravity is strong enough to wobble the star sufficiently for us to detect changes in proper motion or <unk> shift changes in radial velocity ; Jupiter or Neptune sized planets very close to their parent star whose transit causes changes in the luminosity of the star ; or planets which pass in front of background stars with the planet @-@ parent star separation comparable to the Einstein ring and cause gravitational <unk> . Measuring light intensity during the course of a transit , as the planet blocks out some of the light , is potentially much more sensitive , and might be used to find smaller planets . However , extremely precise measurement is needed : for example , the transit of Venus causes the Sun 's light to drop by a mere 0 @.@ 001 magnitude , and the dimming produced by small extrasolar planets will be similarly tiny . 
