For those following this topic, this apparently is the new name of the G1.9 Brown Dwarf Star that Spanish Astronomers claimed the discovery of last summer (see post here: http://t.co/shYC8Fk ).
And it's apparently not a new discovery (NASA P/R again ?) since this article dated last April already mentioned the whole Nemesis/Tyche story: http://bit.ly/cVXSOs
Per Wikipedia, "The use of the name "Tyche" for the planet may also be a reference to an earlier theory of the Solar System's structure that involved the Sun having a dim companion named Nemesis as it was proposed as a cause for mass-extinctions on Earth. Tyche was the name of the sister of Nemesis." http://bit.ly/es1eE5