Q&A: Dark Matter

Q:
About the "dark matter" that is being searched for; I was wondering if it would be possible for some of the missing mass to be in the form of extra-solar planets? They seem to be much bigger than Jupiter and are being found more frequently as of late, and I'm sure they will be found regularly in the future. If even two-thirds of stars have the possibility for a planetary system around them, that should add up to something substantial, right?

A:
The extrasolar planets that have been found so far are very interesting, but unlikely to explain the dark matter. Most are comparable to Jupiter, which has a mass of about 0.001 solar mass. If planets are to account for the dark matter, there would have to be several thousand of them around every star!