Because our Sun is basically a giant ball of flame - and one we should be thankful for, because it keeps us all alive and warm - we've been conditioned to think that all stars are the same; massive fiery balls of gas that exist to provide heat and light for any planets in orbit around them. But this isn't the case.
There is a category of stars known as brown dwarfs, and to all intents and purposes they're failed stars. They have the requisite size, but lack the density required to begin fusing atoms, and therefore they can't burn for very long. Eventually they flicker out and cool down, with the coldest ones detected so far being around 80 degrees Fahrenheit; that's cooler than the human body, and cold enough to touch with the human hand. Because they emit no light, and exist in darkness, brown dwarfs are very hard to detect, showing up only on infrared telescopes, and even then, only when we're specifically looking for them. As such, some scientists believe they may be the components of mysterious 'dark matter'.