Hubble at 35: The Telescope That Changed How We See the Universe

The Hubble Space Telescope launched on April 24, 1990, and immediately revealed a catastrophic problem: its primary mirror had been ground to the wrong shape — off by 2.2 micrometers, 1/50th the width of a human hair — producing blurry images that made it the butt of late-night jokes worldwide. The fix required a spacewalk to install corrective optics, essentially contact lenses for a $1.5 billion telescope.

The repair was executed in December 1993 by astronauts Story Musgrave, Jeffrey Hoffman, and their crewmates. It succeeded. And what followed over the next three decades transformed our understanding of the universe.

What Hubble Changed

The age of the universe. Before Hubble, the age of the universe was estimated anywhere from 10 to 20 billion years — a genuinely enormous uncertainty. Hubble's precise measurements of Cepheid variable stars in distant galaxies allowed an accurate determination of the Hubble constant, pinning the universe's age at 13.8 billion years.

The accelerating universe. The discovery of dark energy — the observation that the universe's expansion is accelerating rather than decelerating — depended critically on Hubble observations of Type Ia supernovae at cosmological distances. The 2011 Nobel Prize in Physics went to the team that made this discovery.

Supermassive black holes are ubiquitous. Hubble observations demonstrated that supermassive black holes reside at the centers of essentially all large galaxies, and that the black hole's mass correlates with the host galaxy's properties — suggesting co-evolution between galaxies and their central black holes.

Deep field images. The Hubble Deep Field (1995), Hubble Ultra Deep Field (2004), and Hubble eXtreme Deep Field (2012) — each a long exposure of what appeared to be empty sky — revealed thousands of galaxies, some from the universe's first billion years. The universe is not empty; every direction contains an unimaginable number of galaxies.

Hubble and Webb Together

Hubble and Webb are complementary rather than redundant. Hubble observes primarily in ultraviolet and visible light; Webb in infrared. Together they provide coverage across a wider range of the electromagnetic spectrum than either alone. NASA plans to operate Hubble as long as possible — potentially into the 2030s — alongside Webb.