When the roiling nuclear fusion inside of a star begins to die — gravity crushing into the star's waning fuel-store of hydrogen atoms, fusing them into heavier helium nuclei — the universe usually offers that star a couple of dignified options for meeting its end.
After its collapse and supernova finale, a star can become a dwarf (our sun's likely retirement), its quieted core a celestial memorial to past glory, aglow in the soft fading of residual heat. Or a star can collapse so dramatically it becomes a black hole. The weirdest stars, though, become neutron stars — dead stars so powerfully dense that even a single teaspoon of their material would have the same mass as 900 Great Pyramids of Giza.
