‘Xeelee construction material,’ Dano whispered. ‘It’s like no other material we’ve encountered. You can’t cut it, bend it, break it. Even if we could build a sphere around a star and set it spinning in the first place, it would bulge at the equator and tear itself apart. But this shell is perfectly spherical, despite those huge stresses, to the limits of our measurements. Some believe the construction material doesn’t even belong to this universe. But it can be shaped by the Xeelee’s own technology, controlled by gadgets we call “flowers”.’
-Resplendent, "Lakes of Light"