Makemake is about a fifth as bright as Pluto. However, despite its comparative brightness, it was not discovered until well after a number of much fainter KBOs had been detected. Most of the scientific hunts for minor planets are conducted relatively close to the region of the sky that the Sun, Earth's Moon, and planets appear to lie in (the ecliptic). This is because there is a much greater likelihood of discovering objects there. Makemake is thought to have evaded detection during earlier searches because of its relatively high orbital inclination, as well as the fact that it was at its greatest distance from the ecliptic at the time of its discovery--in the northern constellation of Coma Berenices.
So here you have two definitions of a blue moon but the one for a calendar blue moon does not describe the true meaning of a blue moon. Here's why:
Using computer models, the team of scientists came up with a complex interior structure for Ganymede, composed of an ocean sandwiched between up to three layers of ice--in addition to the very important rocky seafloor. The lightest ice, of course, would be on top, and the saltiest liquid would be heavy enough to sink to the bottom. Furthermore, the results suggest the existence of a truly weird phenomenon that would cause the oceans to "snow" upwards! This bizarre "snow" might develop because, as the oceans swirl and churn, and frigid plumes wind and whirl around, ice in the uppermost ocean layer, called Ice III, may form in the seawater. When ice forms, salts precipitate out. The heavier salts would then tumble down, and the lighter ice, or "snow," would flutter upward. The "snow" would them melt again before reaching the top of the ocean--and this would possibly leave slush lurking in the middle of the moon's odd sandwich!