March 6 1079

Omar Ibn Ibrahim Al-Chajjam completed Jalali Calendar

Omar has an observatory where he made astronomical tablets, and reformed the calendar, as a result his of his observations he determined the set length of the year to be 365.24219858158 days long. these results are in line to the fifth decimal place with the latest findings of modern astronomy. 

February 18 1930

US Astronomer Clyde Tombaugh Discovers Pluto

Clyde William Tombaugh (February 4 1906 - January 4 1997) was an American astronomer. Although he is best known for his discovery in 1930 of the Dwarf Planet Pluto, the first object to be discovered in what would later be identified as the Kuiper Belt, Tombaugh also discovered many asteroids; he also called for serious scientific research of unidentified flying objects.