A fringe theory posits that one of these objects sends objects from the Oort cloud into the inner Solar System, which in turn causes mass extinctions on Earth; that one is the alleged twin star of the Sun called Nemesis.
Many of these objects are expected to be detected by NASA's WISE infrared space telescope. Gliese 229B was determined to be one of these objects through the detection of methane in its atmosphere, but a more common method to detect these objects is the lithium test. The spectral classes T, L, and Y were created in order to classify these objects, which appear on the absolute bottom right of the HR diagram. A fringe theory posits that one of these objects sends objects from the Oort cloud into the inner Solar System, which in turn causes mass extinctions on Earth; that one is the alleged twin star of the Sun called Nemesis. For 10 points, identify these low mass "failed stars," which are not massive enough to fuse hydrogen in their cores.
Many of these objects are expected to be detected by NASA's WISE infrared space telescope.
 brown dwarfs