No: https://www.reddit.com/r/askscience/comments/gnq8t/is_it_true_that_jupiter_is_a_failed_star/ https://www.reddit.com/r/askscience/comments/gnq8t/is_it_tru...

No: https://www.reddit.com/r/askscience/comments/gnq8t/is_it_true_that_jupiter_is_a_failed_star/ https://www.reddit.com/r/askscience/comments/gnq8t/is_it_tru... The question itself is weird; planets don't really "fail" to become something else. They simply accumulate mass during accretion, and either that mass (and other factors) is sufficient for ignition and sustained fusion, or not. It would be a little bit like asking if Neptune is a failed Jupiter or Mars was a failed Earth (hmm, perhaps a bad example). Jupiter is far, far too small to have been a candidate for a brown dwarf.