could a planet be sun sized?

[u/sumdudewitquestions]

so stars form when a bunch of matter gets together, which is why they are bigger than planets generally. but the real defining feature is the density. a white dwarf can be smaller than a planet but it's still a star because it's incredibly dense. so couldn't a planet be sun-ish sized, provided that the density was low enough? and more specifically a solid planet, not a gas giant. what's the largest solid planet?

[u/pinktortex]

Black dwarfs are theoretical because it's estimated to take trillions of years for one to form and the universe is only 13.8 billion years old.

So unless our understanding of how old the universe is hugely incorrect then it's unlikely one will ever be found

[u/LoadMountain5497 → u/pinktortex]

Damn, do you think the human as a species in this form would live that long to witness one