Twenty years after it first reached space, the Hubble Space Telescope still tirelessly circles the Earth, snapping images of the cosmos and continuing to fulfill its role as the beloved Comeback Kid of celestial imaging.
"I don't think anybody thought Hubble would be around this long. It's sort of like the little engine that could," says Kevin Marvel, executive officer of the American Astronomical Society, in Washington, D.C. "It's just produced result after result after result."
The venerable telescope blasted off inside space shuttle Discovery back on April 24, 1990, and the crew of astronauts deployed the telescope the next day.
Since then, the orbiting telescope has become an object of public fascination — in part because it's repeatedly faced possible failure followed by total triumph, but mostly because of its seemingly endless production of mind-blowing snapshots of supernovae, nebulae and far-away galaxies.
Mesmerizing Images
In celebration of the telescope's 20 years in space, for example, NASA has released a new Hubble photo of the Carina Nebula, a region of our galaxy where stars are being born.
Such mesmerizing scenes have become a part of popular culture over the last two decades, gracing everything from textbooks to postage stamps to coffee cups.
Marvel says that people seem to truly love this telescope. "That has always floored me and I think that's really the true accomplishment of Hubble," he says. "It's managed to take discoveries and knowledge about the universe and make them relevant and important to the American people."
It wasn't always this way. Astronomers had longed for a large orbiting observatory located above the Earth's atmosphere, which can distort light. But soon after the telescope was launched, NASA realized that its main mirror had a serious flaw. All of the images came back fuzzy. This "Hubble trouble" turned the multibillion-dollar telescope into a laughingstock.
100 Times Stronger Than Its Early Days
"After the launch of Hubble we went from being a media star — everybody was anticipating the great science — to what the media called 'the great American disaster,'" NASA's head of science Ed Weiler recalled recently. "Our neighbors were walking up to us and saying, 'Gee, we really feel sorry for you.'"
"I thought that this was a disaster, to be honest, that was my first reaction," says Mario Livio, an astrophysicist at the Space Telescope Science Institute in Baltimore.
But engineers on the ground quickly modified a spare camera to compensate for the mirror's flaws. When astronauts installed that new camera, along with other modifications, in 1993, the images that came back were perfect. And Hubble's long run of science began. So far, it's observed more than 30,000 targets and has collected more than half a million pictures in its archive.
Astronauts have repaired and refurbished the telescope five times. It looked like its last servicing mission would be canceled because of concerns about the safety of the space shuttles in the wake of the Columbia disaster in 2003 — a prospect that dismayed scientists. But NASA officials reconsidered and the final servicing mission, in May of last year, made the telescope 100 times more powerful than when it was launched, according to NASA.
'Revolutionizing Astronomy'
Hubble's discoveries over the years have helped astronomers understand everything from how stars form in our own galaxy to the composition of the atmospheres of planets outside our solar system. Its "Ultra Deep Field" image revealed the most distant objects in the universe. The telescope has also contributed to the study of dark energy and the understanding that the expansion of our universe is speeding up, says Livio.
"Hubble has touched literally on every area of astronomy and astrophysics today. It has really revolutionized astronomy," says Livio. "I would say Hubble exceeded all expectations."
The most recent repairs are expected to keep Hubble going for another five years or so. Because NASA is focused on building a successor to Hubble, the James Webb Space Telescope, no additional servicing missions are planned.
At some point, the telescope will break down. Eventually, NASA expects to deorbit it and send it crashing down over the Pacific.
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