Brown dwarfs are celestial objects that were a little bit too small to develop into proper stars. That doesn’t mean that they can’t be hot – under some circumstances, fusion reactions can still take place inside them just like in our Sun, only at a smaller extent or with different initial products, such as deuterium instead of hydrogen. For astronomers, they are very interesting, because they might offer any planets orbiting them even better chances of life than for larger red dwarfs, which, unfortunately, tend to have strong outbursts of radiation.
Brown dwarfs, on the other hand, are relatively cold, but cozy. A planet would only need to settle in close enough to it to be able to develop life-friendly conditions on its surface. This is precisely the setting for Luhman-16, a double object made of two brown dwarfs, in my upcoming novel “Marchenko’s Children.”