Vera Rubin, American astronomer (born 1928)

Vera Florence Cooper Rubin was an American astronomer who pioneered work on galaxy rotation rates. She uncovered the discrepancy between the predicted and observed angular motion of galaxies by studying galactic rotation curves. Her work on the galaxy rotation problem produced the first widely accepted evidence for the existence of dark matter.

December 25 is the 359th day of the year in the Gregorian calendar; six days remain until the end of the year.