April 22, 2015 7:00 AM EDT

The best space machines reveal their purpose with a single glance. The gangly, leggy lunar module could only have been a crude contraption designed to land on another world. A rocket, any rocket, could only be a machine designed to fly—fast, high and violently.

And so it is with the Hubble Space Telescope—a bright silver, 43 ft. (13 m) long, 14 ft. (4.2 m) diameter cylinder, with a wide open eye at one end and a flap-like eyelid that, for practical purposes never, ever closes. Since shortly after its launch on April 24, 1990, that eye has stared and stared and stared into the deep, and in the 25 years it’s been on watch, it has revealed that deep to be richer, lovelier and more complex than science ever imagined.

Hubble started off sickly, a long-awaited, breathlessly touted, $1.5 billion machine that was supposed to change astronomy forever from almost the moment it went into space, and might have too if its celebrated 94.5 in. (2.4 m) primary mirror that had been polished to tolerances of just 10 nanometers—or 10 one-billionths of a meter—hadn’t turned out to be nearsighted, warped by the equivalent of 1/50th the thickness of a sheet of paper. It would be three and a half years before a fix could be devised and built and flown to orbit and shuttle astronauts could set the myopic mirror right. And then, on January 13, 1994, the newly sharpened eye blinked open, the cosmos appeared before it and the first of one million observations the telescope has made since then began pouring back to Earth.

Some of Hubble’s images have become cultural icons—Pillars of Creation, the Horsehead Nebula. Some have thrilled only scientists. All have been mile-markers in the always-maturing field of astronomy. The fifty images that follow are just a sampling of the telescope’s vast body of work. Hubble still has close to a decade of life left to it. That means a great deal more work and a great many more images—before the metal eyelid closes forever.

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Write to Jeffrey Kluger at jeffrey.kluger@time.com.

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