black holes are absolutely one of the most fascinating objects in this universe. neutron stars are an honorable mention. imagine the entire 1.5 times the mass of the sun compacted into a space 10 miles wide (the size of manhattan). it's basically a giant neutron. it spins sometimes hundreds of times per second. i just watched a show about them and it said that one tablespoon would weigh about a billion tons. wild stuff.

Neutron star - Wikipedia, the free encyclopedia