The Hubble Space Telescope has taken breathtakingly clear pictures of galaxies colliding, suns forming and stars exploding. Paradoxically, the Hubble's clear view has made the universe seem even more mysterious. But now, after 19 years in orbit and more than half a million pictures, the aging Hubble is crippled. One of its sophisticated cameras has failed, and so has a key device called a spectrograph. A computer on board has faltered. So today, NASA hopes to launch the last space shuttle mission to the Hubble, the fifth and likely last time astronauts will visit. It's a cosmic repair job that could provide several more years of discoveries. That's if it succeeds. Getting the Hubble back up to speed will take five space walks. On one of them an astronaut will remove 100 screws from a device that was never meant to be repaired — all in weightlessness. "It looks like a marathon and it is," said astronaut John Grunsfeld, lead spacewalker on the mission. "But it's at a sprint pace."
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The Hubble launched aboard a shuttle in 1990 and instantly overcame a problem that has plagued every astronomer since Galileo: Earth's atmosphere clouds and distorts what people can see through telescopes, even on the clearest nights.
By orbiting above Earth, the Hubble peers far above the atmosphere, straight into the heavens. But just after the 1990 launch, no one could brag about a grand new era of astronomy, because scientists made an agonizing discovery about the $1.5 billion telescope.
Instead of brilliantly detailed pictures, the Hubble's images were blurry. Amazingly, the telescope's mirror had been ground incorrectly.
Embarrassing headlines (and jokes by late-night comedians) followed: "Scientists assess the Hubble loss" (New York Times); "Hubble Question: How could it be?" (Orlando Sentinel); "Hubble Troubles: The gang at NASA can't get the hang of it anymore" (The Oregonian).
But astronauts went back to the Hubble in 1993 and installed a device that fixed the problem. Since then, images have been dramatic: the red, orange, blue and green filaments of the Crab Nebula; the wispy spiraling arms of the Whirlpool Galaxy; and "deep field" images that show thousands of galaxies, each of which contains millions or billions of stars.
But when astronomers talk about the Hubble, they don't gush over the pretty pictures. In fact, Hubble's biggest contribution may be that it has shown scientists how much of the universe we can't see at all.
For example, the mysterious force known as "dark energy."
Nobody was looking for dark energy before Hubble. Instead, astronomers were hoping to use Hubble's precise observations to learn how fast the universe is expanding. So they aimed it at certain types of exploding stars, and made some calculations.
They were shocked to discover stars and galaxies are now expanding even faster than they were billions of years ago, closer to the time of the Big Bang.
The only way to explain this, physicists concluded, is that some form of energy must be spreading galaxies farther and farther out — but not a kind of energy we can see, like a flame on Earth. Hence the name "dark energy." It's now one of the great unanswered questions of physics.
"Nobody could have predicted that one," said Ray Villard of the Space Telescope Science Institute, which coordinates Hubble research.
Hubble also searched for "dark matter."
That was a difficult trick, because this was a largely theoretical concept about a substance no one could see. Physicists believed invisible matter must exist because without it, there wouldn't be enough gravity to hold galaxies together.
University of Florida professor Anthony Gonzalez was part of a team that used Hubble and other telescopes to go hunting for dark matter. To do it, they looked at light shining from behind the Bullet Cluster of galaxies. By the laws of physics, light can actually be bent by gravity when it passes by massive objects such as planets or stars.
But light passing by the Bullet Cluster bent even more than it should have, considering the mass of the stars and gases in the cluster. Something invisible had to be present to bend the light so much — the dark matter they were looking for.
Like other telescopes, Hubble actually sees into the past. It can see more than 13 billion light years away. And because a light-year is the distance it takes for light to travel in one year, this means Hubble has seen what portions of the universe looked like 13 billion years ago.
That's one of the mind-boggling aspects of the Hubble's images.
The light of those stars "has taken almost the age of the universe to travel across the universe," Villard said.
Curtis Krueger can be reached at firstname.lastname@example.org or (727) 893-8232.