Super-Jovian planet. Computer artwork of a large gas giant planet (left) orbiting a star. Numerous such planets, with masses greater than that of Jupiter, have been discovered orbiting nearby stars. Most orbit close to their sun and so have very high surface temperatures. Some may be massive enough to be considered brown dwarf stars. A brown dwarf can be considered a cool star, or a large planet, that is insufficiently massive for nuclear reactions to start. Instead, it shines faintly, mostly by infrared radiation, as it slowly collapses by gravitational contraction. It would be similar to Jupiter, the largest planet in our solar system, which also radiates in this way.