On October 21, 2003, a photograph of the nocturnal sky was taken, where almost 2 years later, in January 2005, evidence was raised that there might be a 10th planet at the borders of our solar system: Eris, located in the Kuiper Belt and named after the Greek godess of discord.
On this day in 1994, the last parts of the comet Shoemaker-Levy 9 collided with the largest planet within our solar system, Jupiter. This was the first time, that an extraterrestrial collision of two objects could be directly observed.