Planet-like Object May Have Spent Its Youth as Hot as a Star

A four-stage sequence (left to right) showing the possible extreme temperature evolution for WISE J0304-2705. For about 20 million years, the object was as hot as a star, shining with a temperature of at least 5,100 degrees Fahrenheit (2800 degrees Celsius). After about 100 million years it had cooled to about 2,700 degrees Fahrenheit (1500 degrees Celsius), and by a billion years its temperature was about 1,800 degrees Fahrenheit (1000 degrees Celsius). The final stage is billions of years later, when WISE J0304-2705 has cooled to its current planetary temperature of 100-150 C.