Hubble Space Telescope (NASA/ESA, 1990)

Hubble Space Telescope transformed astronomy after a flawed launch in 1990 required corrective optics via a 1993 Space Shuttle mission. Its 1995 Hubble Deep Field image captured 3,000 galaxies in a patch of sky the size of a grain of sand, proving over 100 billion galaxies exist. Measurements of distant supernovae by Hubble in 1998 led to the 2011 Nobel Prize, revealing dark energy constitutes 68% of the universe. Faster than the average telescope at imaging data, Hubble’s 2.4-meter mirror produced findings that remake cosmology—outperforms #4’s prior telescopes by quantifying cosmic acceleration, a data point cemented by its 30-year, 1.5 million observation legacy.