Brown Dwarves and Nemesis

A reader sends along two articles, one about a "'star' is so cold that any residents on an orbiting planet would see a dark sun in their starry 'daytime' sky" — 'Dark sun' is one of our nearest neighbours — and the other speculating that "[a] dark object may be lurking near our solar system, occasionally kicking comets in our direction" — Getting WISE About Nemesis.