Mirror matter is predicted to exist if parity is an unbroken symmetry of nature. Currently, there is a large amount of evidence that mirror matter actually exists coming from astrophysics and particle physics. One of the most fascinating (but speculative) possibilities is that there is a significant abundance of mirror matter within our solar system. If the mirror matter condensed to form a large body of planetary or stellar mass then there could be interesting observable effects. Indeed studies of long period comets suggest the existence of a solar companion which has escaped direct detection and is, therefore, a candidate for a mirror body. Nemesis, hypothetical ``death star'' companion of the Sun, proposed to explain biological mass extinctions, may potentially be a mirror star. We examine the prospects for detecting these objects if they do indeed exist and are made of mirror matter.