HD 149026b is a sweltering 3,700 degrees Fahrenheit (2,040 degrees Celsius), so hot that astronomers believe it is absorbing almost all of the heat from its star, and reflecting very little to no light. Objects that reflect no sunlight are black. Consequently, HD 149026b might be the blackest known planet in the universe, in addition to the hottest. Credit: NASA/JPL-Caltech
