Funny that by this measure, black holes get less dense as you pile stuff into them.
perhaps it is dying from hawking radiation considering it is so old (about 13b years)
I think given the current level of cosmic background radiation (3K if I remember correctly) any black holes larger than 0.1 mm (just less than the mass of the moon) will get larger over time rather than smaller.
It's only once the universe cools down to below their surface temperature that they'll start evaporating.
Are you saying the nucleus? because hydrogen is too