These 36 galaxies are some of the 40+ that have been observed by astronomers using the Hubble Space Telescope because they contain both Cepheid variable stars and supernovae. These stars are used measure the distance and refine the measurement of the rate of the expansion of the universe. Pictured above (from left to right and top to bottom) are NGC 7541, NGC 3021, NGC 5643, NGC 3254, NGC 3147, NGC 105, NGC 2608, NGC 3583, NGC 3147, Mrk 1337, NGC 5861, NGC 2525, NGC 1015, UGC 9391, NGC 691, NGC 7678, NGC 2442, NGC 5468, NGC 5917, NGC 4639, NGC 3972, The Antennae Galaxies, NGC 5584, M106, NGC 7250, NGC 3370, NGC 5728, NGC 4424, NGC 1559, NGC 3982, NGC 1448, NGC 4680, M101, NGC 1365, NGC 7329, and NGC 3447.

Image Credits: NASA / ESA / STScI