Most galaxies in our universe are bound together into clusters that dot the cosmic landscape like urban sprawls, usually centred around one old, monstrous galaxy containing a massive black hole.

We have adopted the method to place a hollow rigidity axle (with hole and ridge) in the bamboo curtain reel to proceed bound drying, which can improve drying velocity and drying quality effectively.

The identification of an object as a black hole requires the further assumption that no other object (or bound system of objects) could be so massive and compact.