Orbiting 350 miles above Earth for the past 19 years, the Hubble Space Telescope has allowed scientists to peer deep into the cosmos, sending them astonishing images of newborn stars and colliding galaxies from the earliest moments of the universe.
But there's more than meets the eye for this ground-breaking telescope.
How much do you really know about the beloved Hubble? Here are 10 things you probably don't know yet.
1. NASA's "Comeback Kid" started out as a failure.
Now, it's an international sensation, widely known as the "people's telescope." But that wasn't always the case.
"It is now viewed as this unqualified success that has transformed our knowledge of the universe," said Roger Launius, senior curator for the Smithsonian's National Air and Space Museum in Washington, D.C. "I've heard it compared to, in terms of its impacts, the same level of change as when Galileo first turned his homemade telescope on Jupiter in 1609."
But "the telescope began life being viewed as a flop," he said.
A measuring error in the grinding of the mirror prevented the telescope from focusing light properly. As a result, soon after its launch in April 1990, the photos sent back to Earth were fuzzy disappointments.
Hubble's $3 Billion Flaw
The mirror was ever so slightly the wrong shape, which caused light that bounced off the center of the mirror to focus in a different place than the light bouncing off the edge. The flaw was minuscule -- 1/50th the thickness of a sheet of paper -- but it made a significant difference.
"[There were] NASA scientists that stood up and said, "It's a total loss," Launius said of Hubble's early days.
Members of Congress, including Sen. Barbara Mikulski, D-Md., who was, and still is, a big NASA supporter, were livid that this had taken place.
"This was such a failure, to the tune of $3 billion," he said.
Thankfully, the telescope's first servicing mission in December 1993 was a success. After spending 11 months training for what is considered to be one of the most complex missions, astronauts installed a series of small mirrors to fix the flaw.
"They had figured out some ways to work around that problem," Launius said. "But it took a while to generate some of the images that we've seen."
In Hollywood, Hubble's a Star, Too
2. Like us, Hubble can't look directly at the sun.
Hubble has photographed every planet in the solar system, with one exception: Mercury.
The solar system's innermost planet is too close to the sun for Hubble to observe. The sun's bright light would permanently damage its optics and electronics.
Mercury's angular separation from the sun is always less than 28 degrees, which means that it's never out of the sun's glare and, therefore, off limits for the Hubble.
3. It's a pop-culture icon.
Hubble and its images have also had their share of cameo appearances in Hollywood flicks and TV shows.
When "Naked Gun 2 1/2" came out in 1991, Hubble was still a national laughingstock.
In the movie, it was pictured in the Blue Moon Cafe on a wall of failures, smack in the middle of the Titanic and the Hindenberg.
Imagery from Hubble has also been spotted in the movies "Happy Feet" and "Contact."
For the album cover of its 2000 release "Binaura," Pearl Jam used an image of Hubble's "Hourglass Nebula."
The 'Pioneer of the Distant Stars'
4. Hubble's namesake almost chose the law over astronomy.
When the U.S. Postal Service released a special 41-cent for Edwin Hubble in 2008, they called him a "pioneer of the distant stars."
But Hubble was close to choosing another path for himself. Born in Missouri in 1889, Hubble studied math and astronomy as an undergrad but then went on to study law as one of the first Rhode Scholars at Oxford University.
He reportedly moved to Kentucky to practice law. But the pull of the cosmos was too great. Hubble spent most of his career at California's Mt. Wilson observatory.
He is credited with many discoveries but most notably for observing that the farther apart galaxies are from each other, the faster they move away from each other. Based on this, Hubble concluded that the universe expands uniformly.
When the Hubble Space Telescope launched, one of its goals was to figure out this expansion rate, called the Hubble Constant.
Hubble Images as Works of Art
5. Hubble images are held from the public for one year.
In its 19-year-career, Hubble has made about 880,000 observations and has released about 570,000 images of the universe.
But before any of those images are shown to the public, they are held in a proprietary waiting period. For one year, the scientist (or scientists) involved in the project that took the image have the exclusive opportunity to review the data.
Scientists can elect to forego the waiting period but, the research world being as competitive as it is, that rarely happens.
6. Hubble's masterpieces have debuted at the museum.
Not only has Hubble penetrated Hollywood, it has also found its way into the rarefied world of the fine arts.
Science aside, many of Hubble's images are astoundingly beautiful. The Walters Art Museum in Baltimore displayed a number of Hubble's iconic images last year in the exhibit "Mapping the Cosmos: Images from the Hubble Space Telescope."
More than 20 images were on display at the museum.
"It is really gratifying to see these pictures, constructed from Hubble's science data, among the beautiful, classical art in the Walters Art Museum," Zoltan Levay, senior image processor at the Space Telescope Science Institute in Baltimore, said at the time. "I hope visitors can enjoy the images as photographs of the cosmic landscapes, but also as artistic abstractions from nature."
7. It has more than 3 billion miles under its belt.
Every 96 minutes, Hubble makes one orbit around Earth. In its lifetime, it has circled Earth more than 100,000 times, traveling about 5 miles per second. In all, the space telescope has traveled more than 3 billion miles, which is about the distance from Earth to Pluto.
How Do Scientists Score Time with Hubble?
8. Scientists have to apply for QT with the HST.
Everyone wants a piece of the Hubble, but it only has 3,000 available hours each year. To divvy up the time, a panel of internationally renowned scientists at the Space Telescope Science Institute reviews proposals submitted by teams of scientists around the world.
"The proposals are ranked according to, in their opinion, what is the most challenging, the most important, what science can be gained from these proposals," said Cheryl Gundy, the institute's deputy news manager. "The director of the institute makes the final decision, parceling out the Hubble's time."
Some teams may only get a couple of minutes with the telescope, but even a window of time that small is highly coveted.
9. As far as telescopes go, Hubble is only average-sized.
It looks large when we see the school-bus sized telescope next to the floating astronauts. But NASA scientists say it's actually not that big for a telescope.
Hubble's primary mirror is about 8 feet in diameter, much smaller than the 34-foot mirror in the world's largest telescope, the Great Canary Telescope on the island of La Palma, part of the Canary Islands. The mirror for the Keck telescope in Mauna Kea, Hawaii, is about 25 feet.
"It's very average," said Malcolm Niedner, the Hubble deputy senior project scientist. "I'd love to have it in my backyard but it's not a large telescope."
But Hubble makes up for its size with incredible optics and design. Most importantly, Niedner said, its placement outside Earth's atmosphere enables it to see greater distances with greater clarity than any other telescope.
Hubble's Golden Years10. Hubble is preparing to hand the reins over to its successor.
The massive Hubble makeover is expected to give the space telescope about five more years. If all goes according to plan, it should retire just as astronauts launch the heir to NASA's space telescope throne: The James Webb Space Telescope.
Slated for launch in 2014, the replacement telescope will have a mirror 21.3 feet in diameter and a sunshield the size of a tennis court.
As opposed to Hubble's humble 350 mile orbit, the Webb telescope will orbit 1 million miles from Earth, which means that the days of risky servicing missions, for better or for worse, will end with Hubble.
But the telescope, named for James E. Webb, NASA's second administrator, will be able to explore the most distant galaxies and give scientists even more information about the earliest moments of the universe.