I just learned about Brown Dwarfs, they are "failed" stars, they narrowly missed the stellar mass mark. I learned that Y Dwarfs have temperature as low as 80 Fahrenheit (The first one found by WISE observatory), why aren't those not called a Jupiter-like planets without a host star? Why do we call them a star and designate a separate category for them (T or Y)?
Ok suppose T and Y dwarfs are okay, let's leave them alone. But why can't Jupiter be a Y Dwarf who is in the binary relationship with the Sun? Sun-Jupiter's Barycenter is just outside the Sun, we could call them in orbit with each other correct?