Almost everyone has probably seen that famous photograph space at one point or another — the “Pillars of Creation” — three towering gas and dust columns, light-years long in their height, rising up against the greenish backdrop of space. That was just one of many iconic photos taken by the Hubble, the largest and most versatile space telescope in existence — and one that for the most part has been assembled and enhanced, piece by piece, in space. The telescope was conceived by NASA in 1974 as a “Large Space Telescope” and funded in no small part by the European Space Agency, in exchange for 15% telescope time.

On this day, April 24, in 1990, after a two-year moratorium on launches following the Challenger disaster, the Space Shuttle Discovery went up, carrying with it the Hubble Space Telescope on board. The two years were spent productively by the Hubble team, upgrading communications equipment and the power-producing solar array.

The telescope was named after Edwin Hubble, the scientist who first posited that the universe was expanding, and created a formula for the velocity of outer galaxies. The telescope itself, free from the interference of the atmosphere, was able to take more precise readings of the outer galaxy speeds, which enabled scientists to gain a better estimate of the age of the Universe (between 9  and 14 billion years). The Hubble measurements were one of the landmark recent findings in the field of astronomy.