 As we continue to add mass, the planet creates densities much greater than lead. The core becomes so hot and dense that, at around 11 to 16 Jupiter masses, it starts to fuse deuterium. At this point, it begins to shine in infrared wavelengths. We no longer have a planet, we have a brown dwarf. Glease 229B is a brown dwarf. Being larger than hat P2B tells us that it contains a smaller amount of heavier elements. It's 70% larger than Jupiter, but has 45 times its mass. It's important to note that at these masses, celestial objects cannot fuse hydrogen or lithium. And the thermal forces created by the deuterium burning are not enough to break the hold created by electron pressure.