Esko Jorma Johannes Valtaoja (pronounced [ˈesko ˈʋɑltɑˌojɑ]; born 20 June 1951) is a Finnish professional astronomer and writer. Valtaoja worked as a professor at the University of Turku where he studied quasars. Valtaoja retired in 2015 after holding a popular farewell lecture, that was also televised by Finnish national public broadcaster YLE. According to the Finnish Science Barometer conducted in 2013, Esko Valtaoja was the most well known Finnish scientist in Finland. In his free time he enjoys art and literature (especially science fiction). He is also an amateur biologist.