[oPerrin]

An interesting point from the wikipedia articles: One version of the theory, that the nemesis star is a brown dwarf, should be testable in the next year or so. The WISE mission is launching in just over 33 days, and its year long mission will detect any brown dwarf stars within 2-3 parsecs of us, which is within the suggested range for nemesis.

http://wise.ssl.berkeley.edu/