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The Hubble Space Telescope Can See 13.4 Billion Light-Years Away — Near the Edge of the Observable Universe
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The Hubble Space Telescope Can See 13.4 Billion Light-Years Away — Near the Edge of the Observable Universe

March 28, 2026 · 4 min read

The Fact

The Hubble Space Telescope can see objects up to 13.4 billion light-years away.

The Hubble Space Telescope was launched in April 1990 and almost immediately discovered to have been ruined before it ever operated. The primary mirror, 2.4 meters in diameter, had been ground to precisely the wrong shape — off by just 2.2 micrometers at its edge, a distance less than one-fiftieth the width of a human hair. This tiny error produced catastrophically blurry images. A mirror polished to nanometer precision using the most sophisticated optical technology of the era had been calibrated against a measurement tool that contained a small lens incorrectly positioned, systematically skewing every measurement across the entire polishing process.

The error was fixed in a December 1993 servicing mission, when astronauts installed corrective optics — effectively giving Hubble a pair of glasses — and the telescope became what its designers had envisioned. Since that repair, it has operated as the most productive astronomical instrument in history, contributing to more than 19,000 peer-reviewed scientific papers and transforming humanity's understanding of the universe's age, expansion, and content. The farthest object it has imaged with certainty is a galaxy called GN-z11, located approximately 13.4 billion light-years away.

Looking Back in Time

The concept of looking across space while simultaneously looking back in time is fundamental to all astronomy. Light travels at approximately 300,000 kilometers per second — fast by any earthly standard, but finite. Light from the Sun takes about 8 minutes to reach Earth; light from the nearest star takes 4.24 years. Light from GN-z11 took 13.4 billion years to arrive.

This means that when Hubble's detectors recorded the photons from GN-z11, those photons had been traveling since the universe was approximately 400 million years old — when the first galaxies were only just forming. The image of GN-z11 is not an image of what that galaxy looks like now; it is a fossil record of what a very young galaxy looked like in the early universe, preserved in the light that has been traveling toward us for the entire history of complex cosmic structure.

The Technical Achievement

Detecting a galaxy 13.4 billion light-years away requires overcoming two related challenges: the object is extremely distant and therefore faint, and the universe's expansion has stretched the light emitted by that galaxy dramatically. The redshift of GN-z11's light — the stretching of wavelengths as the universe expanded during the photons' journey — means that light originally emitted as ultraviolet radiation arrives at Earth in the near-infrared portion of the spectrum.

Hubble's near-infrared capability, extended by the Wide Field Camera 3 installed during the final servicing mission in 2009, was what made detecting GN-z11 possible. The observation required looking at the same region of sky for extremely long exposures — the Hubble Ultra Deep Field images, which revealed approximately 10,000 galaxies in a patch of sky the apparent size of a grain of sand held at arm's length, accumulated more than 11 days of total exposure time.

Beyond Hubble

The James Webb Space Telescope, launched in December 2021 and fully operational from mid-2022, has since extended the record for most distant observed objects. Operating in the mid-infrared rather than the optical and near-infrared, JWST has detected galaxy candidates at redshifts corresponding to distances of 13.5 to 13.7 billion light-years — closer still to the cosmic horizon of the observable universe, which lies at approximately 13.8 billion light-years from Earth (the distance light could have traveled since the Big Bang).

Hubble and Webb represent a continuous project of extending human sight through time and space, with each generation of instrument revealing structures and events that previous generations could only theorize. The universe that Hubble opened to view — vast, ancient, filled with hundreds of billions of galaxies — has already been superseded in its far reaches by instruments its makers could barely imagine when it was launched, which is perhaps the most accurate summary of how scientific progress tends to work.

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FactOTD Editorial Team

Published March 28, 2026 · 4 min read

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