How WISE 70304-2705 could have evolved from a star to a “planet-like object”. Credit: John Pinfield,
Nature once again shows us how hard it is to fit astronomical objects into categories. An examination of a so-far unique brown dwarf — an object that is a little too small to start nuclear fusion and be a star — shows that it could have been as hot as a star in the ancient past.
The object is one of a handful of brown dwarfs that are called “Y dwarfs”. This is the coolest kind of star or star-like object we know of. These objects have been observed at least as far back as 2008, although they were predicted by theory before.