January 05

1896 – An Austrian newspaper reports that Wilhelm Roentgen has discovered a type of radiation, later known as "X-rays."
2005 – "Eris," the largest known dwarf planet in the Solar System, is discovered by the team of Michael E. Brown, Chad Trujillo, and David L. Rabinowitz using images originally taken on October 21, 2003, at the Palomar Observatory.

Fun Fact:
Polar bears are almost undetectable by infrared cameras.