Interesting facts:
• Quasars (Quasi-stellar objects) were first mistaken to be stars, but later they were discovered to be galaxies. They have a very high redshift, which means that they are traveling at a speed close to the speed of light!
• At the center of every galaxy, there resides a massive black hole! Even our Milky way galaxy has a massive black hole in its center.
• Mathematically, a black hole is an object of zero size and infinite density (but finite mass)– a singularity.