1) A neutron star is a leftover core from a dead star, composed almost entirely of neutrons. They have masses up to twice that of our sun, but can be about 15 miles in diameter (1/60,000 of our sun). Their density is equivalent to compressing the entire human race into a sugar cube.
2) In the presence of two colliding black holes, spacetime is incredibly stretched and contorted. There exists a specific looping path that you can take around the two objects that puts you in the past of where you began.
3) All the elements in the universe heavier than helium and up to iron were created in the fusion process in the cores of high-mass stars. All the elements heavier than iron were formed upon the ultra-powerful supernova deaths of these stars. These stellar explosions threw the star’s enriched guts across the universe to make the next generation of solar systems like ours. The very atoms that make up your body were created in the cores of stars. As Carl Sagan once said, “we are stardust.”
4) When solar flares are released from our sun, they not only shoot outwards but also snap back, like a breaking rubber band. Sometimes a super-powerful flare’s recoil can cause a phenomenon called a sunquake. The energy of the recoil is equivalent to covering the entire landmass of the Earth with dynamite a yard thick, and setting it off all at once. Circular ripples form on the sun’s surface move outward from the point of impact, like a pebble in a pond. Except that these "ripples" are two miles high, and travel at 250,000 miles per hour.
5) A pulsar is a highly magnetized, spinning neutron star that emits light beams caused by electromagnetic radiation from its two poles. When the poles point towards Earth, we see a pulsating effect, similar to how a lighthouse works. Because their high mass gives them so much momentum, the regularity of pulsation is as precise as an atomic clock. The fastest spinning pulsar ever discovered rotates at 600 times per second, its surface moving at about 18,641 miles per second (10% the speed of light).
6) Quasars are compact regions in the centers of massive galaxies surrounding their supermassive black holes. The energy of material falling into the black hole emits directionalized beams out of its poles. Quasars are ten trillion times brighter than our sun. If you were to count to just one trillion at one number per second, it would take you 31,546 years.
7) Magnetars are neutron stars with magnetic fields so immensely strong that they can kill a person from 600 miles away by warping the atoms of their flesh. Their magnetic fields are one quadrillion (a million billion) times that of Earth’s. On December 27, 2004, a magnetar produced the brightest event from outside our solar system in the history of astronomy. More on this event here.