The Galaxy's Largest Diamond
unassimilatible writes "The Harvard-Smithsonian Center for Astrophysics reports 'to impress your favorite lady this Valentine's Day, get her the galaxy's largest diamond.' A newly discovered cosmic diamond is a chunk of crystallized carbon 50 light-years from the Earth in the constellation Centaurus. It is 2,500 miles across and weighs 5 million trillion trillion pounds, which translates to approximately 10 billion trillion trillion carats, or a one followed by 34 zeros. A cheesy, unrealistic simulation is also available. AP has a story as well."
That's true, the majority of its mass is hydrogen. But you're forgetting just how friggin' massive Jupiter is. Even if only a tiny tiny fraction of a percent were a diamond, it'd still be huge!
Part of Clarke's explanation for this theory (in "2061", actually) explained that Jupiter's high gravity would cause the more massive molecules -- like methane, which Jupiter definitely has in quantity -- would sink through the atmosphere towards the core. And at the core, the intense pressures would separate the carbon from the hydrogen (in the methane), and the hydrogen would waft back up (being of lesser mass), while the carbon would stay in the core.
Think of it as being like a black hole, except without the extreme singularity -- instead of being compressed to a single point, it's being compressed into a diamond. (But it's not just the gravity doing this, it's also the intense atmospheric pressure of all the gasses sitting above the core, too.)