Sasselov has been a professor at Harvard since 1998. He arrived to CfA in 1990 as a Harvard-Smithsonian Center post-doctoral fellow. Between 1999 and 2003 he was the Head Tutor of the Astronomy Department.

Sasselov was born in Bulgaria, and was educated at Sofia University, where he received his PhD in Physics in 1988, almost concurrently working on his degree at the University of Toronto, Canada, where he received his PhD in Astronomy in 1990. His research explores the many modes of interaction between radiation and matter: from the evolution of hydrogen and helium in the early universe to the study of the structure of stars. He is very fond of unstable stars – ones that pulsate regularly and allow us to determine distances to other galaxies. Most recently his research has led him to explore the nature of planets orbiting other stars. He has discovered a few such planets – with novel techniques that he hopes to use to find planets like Earth. He is the director of the new Harvard Origins of Life Initiative – a multidisciplinary center bridging scientists in the physical and in the life sciences, intent to study the transition from chemistry to life and its place in the context of the Universe.