In the summer of 1995, Robert Williams, then director of the Space Telescope Science Institute, which manages the Hubble Space Telescope's research program, was paid two visits by the renowned astronomer John Bahcall, considered one of Hubble's founding fathers.
Bahcall had, in hindsight, a strange request.
He urged Williams not to train the powerful NASA telescope into an uncharted region of space, where the school bus-sized observatory would stare for days in an attempt to observe profoundly distant, never-before-seen galaxies. It was a proposed endeavor to capture an unprecedented "deep field" view of the cosmos, allowing humanity to look back billions of years, near the dawn of time.
Though Bahcall believed Hubble would make many astronomical advances, he didn't think it would observe any new, undiscovered galaxies — even in its lofty position above Earth's image-distorting atmosphere. Crucially, a failed attempt would bring more shame to a telescope that was already an orbiting object of ridicule: After launching in 1990, a flawed mirror captured blurry images in what was then the most expensive science project in history, requiring astronauts to visit Hubble and install a refrigerator-sized instrument to act as Hubble's "correcting eyeglasses."
So Williams knew the deep field was indeed a risk. Still, he told Bahcall he was compelled to take it.
"I told him that I'm willing to fall on my sword," Williams told Mashable.
Soon after those meetings, Williams directed Hubble — which, in April 2025, celebrated its 35-year anniversary of launching — to peer at a seemingly empty patch of space for 10 straight days. The space telescope beamed home iconic imagery, a "cosmic zoo" of some 3,000 galaxies. It changed everything.
"It was mind-blowing," Jennifer Wiseman, a postdoctoral researcher at the time, today the Hubble Space Telescope's senior project scientist, told Mashable. "To actually see thousands of smudges of light — and now we know each of them can contain billions to hundreds of billions of stars and planetary systems — is a feast for the mind."
"It was mind-blowing."
Behold, the central portion of the first Hubble Deep Field. This is a view from a patch of sky the size of a grain of sand held at arm's length.
The endeavor to capture Hubble's Deep Field
The year NASA first landed astronauts on the moon, 1969, was when the first real rumblings of a space telescope began. That year, the National Academy of Sciences published a report called "Scientific Uses of the Large Space Telescope." In the mid-'70s the idea progressed, and by 1977 Congress had approved the first funding for the "Large Space Telescope project," amounting to $36 million. The very next year, work began on Hubble's nearly eight-foot mirror. By 1983, the developing telescope was named for astronomer Edwin Hubble — the scientist who discovered that innumerable galaxies exist in space beyond our Milky Way.
But the same year Hubble launched, in 1990, the astronomer Bahcall released a prominent paper that concluded, in no uncertain terms, "We do not expect HST to reveal a new population of galaxies."
"That really got me worried," Ray Villard, the Hubble Space Telescope news chief who has worked on the mission for decades, told Mashable.
It was worrying that Hubble — decades in planning and at a steep cost — might not break through the galactic boundaries of Earth-based observatories, Villard explained. That would be hard to explain to the public.
"Someone has to try it."
Why might Bahcall, a prominent advocate for the mission, have such dampened hopes? Before launching, Bahcall and other astronomers sought to simulate what Hubble would see, Williams explained. The calculations were complicated, and they required some assumptions, one of which was that galaxies had relatively smooth levels of brightness across their surfaces. But, in fact, they don't. Most galaxies have regions of robust star formation that create luminous areas, allowing powerful telescopes like Hubble to observe them at profound distances. Bahcall's calculations, however, concluded that Hubble was not likely to resolve such distant galaxies.
By 1995, these discouraging expectations were amplified by a hostile cultural climate. Hubble required a Space Shuttle repair mission costing over $1 billion to remedy its blurry cosmic images. "The telescope had become a big joke," Williams said. "Political cartoons lambasted NASA." What's more, if Hubble failed to view farther into space than land-based telescopes, the federal government — the primary financial patron for astronomy — would almost certainly decrease funding for Hubble and reject another such project, at least anytime soon. But Williams, quite simply, swung for the fences.
"If you want to make discoveries, one must take risks," he said. "Someone has to try it."
Even picking a deep field target was a contested issue. Williams wanted to observe a black, largely blank field of space, to avoid a known or prominent object dominating the image. The majority of Hubble's advisory committee disagreed, thinking it was too risky to choose an uncharted region of space. "That was a big debate," Williams recalled. But, as director, Williams had a card to play, known as "Director's Discretionary Time," which can be used relatively sparingly to bypass a long review process.
He played the card. Months later, Hubble viewed a seemingly empty part of space near the handle of the Big Dipper.
Thousands of galaxies popped up in a previously black ether. Where previously ground-based telescopes took humanity about halfway across the universe, Hubble's first deep field took us most of the way, some 12 billion miles (the universe is about 13.7 billion years old).
"Hubble opened up an undiscovered country," Villard marveled.
When the Space Telescope Science Institute revealed the Hubble Deep Field to the public, it was difficult to contain the anticipation. The institute made a 10-foot poster of the cosmic vista, and covered it up for a great unveiling. "People kept peeking under the sheet," Villard said.
The Deep Field was just the beginning
Thirty years later, the deep field's impact hasn't faded.
"Hubble is the first to open our eyes to the full richness of the universe, especially through cosmic time," Wiseman, Hubble's senior project scientist, said.
Crucially, the aging telescope is enabling new and innovative science, including complementary studies with other observatories. "Hubble is actually more scientifically productive now than ever before," Wiseman emphasized, noting the number of scientific papers based on Hubble data is at a record high. Astronomers have used Hubble to detect a rogue black hole, scrutinize the expansion of the universe, advance our grasp of galactic evolution, detect atmospheres on distant exoplanets, and beyond.
Hubble's Deep Field also showed us what to strive for. "Hubble baked the cake," Villard said. Now, powerful observatories like the James Webb Space Telescope, designed to peer beyond Hubble's view, are the frosting.
"Hubble baked the cake."
"We wouldn't even know it was worth looking if it weren't for Hubble's Deep Field," Wiseman said. Webb has now peered back at galaxies formed just some 300 million years after the Big Bang.
More Hubble deep fields followed the 1995 success. And numerous astronaut servicing missions improved the telescope's cosmic-viewing abilities. In 2002, astronauts installed the Advanced Camera for Surveys, or ACS, providing even sharper images. That year, Hubble captured an image of the warped "Tadpole Galaxy," backed by a pond of thousands of diverse galaxies.
"My jaw dropped," Villard said of the 2002 view. "I don't want to get religious, but it was almost god-like vision."
Decades later, the view Williams risked Hubble's public credibility for, and his own, evokes in him the same feeling he gets when peering at the cosmos atop a mountain on a starry, moonless night.
"I am overcome," Williams said.
Staring deeply into the Hubble Deep Field is peering far into cosmic history, a look at these far-off galaxies as they existed billions of years ago. But it's also where we came from, as ancient exploding stars birthed the ingredients for new stars and dispersed the essential ingredients, like the iron in our blood, throughout new realms of the universe. If you look deeply, you're looking at yourself, too.
"We're looking at our origins," Williams said.
