Alexei Filippenko was a member of the Supernova Cosmology Project and
the High-z Supernova Search Team that used observations of extragalactic
supernovae to discover the accelerating universe. This universal acceleration
implies the existence of dark energy and was voted the top science breakthrough
of 1998 by Science magazine.
Alexei Filippenko developed and runs the Katzman Automatic Imaging
Telescope (KAIT), a fully robotic telescope which conducts the Lick Observatory Supernova Search (LOSS), the most successful nearby supernova search. He is also a member of the Nuker Team which uses the Hubble space telescope to examine supermassive black holes and determined the relationship between a galaxy's central black hole's mass and velocity dispersion. The Thompson-Reuters "incites" index ranked Filippenko as the most cited researcher in space science for the ten-year period between 1996 and 2006.