Hubble view of the galaxy cluster Abell 1689. Image credit: NASA / ESA / Hubble Heritage Team / STScI / AURA / J. Blakeslee, Dominion Astrophysical Observatory / H. Ford, JHU. In the 1990s, two groups of astronomers reported their observations that the expansion of the Universe has been accelerating for the last seven billion years. Their conclusions were based on analysis of Type Ia supernovae (SN Ia), which are crucial for the studies of stellar...
