The Hubble Searches for the First Light

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Hubble's Cone Nebula: a pillar of glowing hydrogen and swirling dust

Last March, U.S. astronauts made five of the most challenging spacewalks ever attempted in order to give the venerable Hubble Space Telescope a new lease on life. The new digital camera and solar generators they installed boosted Hubble's optical power tenfold, essentially making it a new telescope with unprecedented reach and clarity.

The first target for Hubble's new eye was an important choice for NASA. The agency wanted to pick a patch of sky that would not only show off the telescope's new muscle for scientists but also produce gasp-inspiring photos for the public. The choice: The so-called Tadpole Galaxy. Earth-based telescopes had captured what appeared to be a galaxy some 420 million light years away that had crossed paths with a dense dwarf galaxy, resulting in a long tail of stars and galactic debris spun off by tidal forces. NASA knew Hubble should be able to show individual stars inside the galaxy, quite a feat at such a distance, about 200 times that of the nearest galaxy to our own Milky Way. It was a conservative choice, though. Visually interesting, scientifically significant, but hardly ground-breaking.

Then, about a month ago, jaws nearly hit the floor when the Tadpole image reached the Space Telescope Science Institute, which operates Hubble under contract to NASA. It was not the Tadpole itself, which looked just fine and about as astronomers had expected it to, but the background of the photo. It was filled with other galaxies. Thousands of them, including one, a faint red smudge in one corner of the picture, that probably is among the oldest objects ever witnessed, formed within about a billion years of the Big Bang itself.

"We knew we had a much better camera, a factor of 10 improvement, but it just shows that we didn't know exactly what that would mean," said Mark Clampin, one of the institute scientists there that day.

Without even trying, Hubble had come tantalizingly close to the Holy Grail of optical astronomy, that moment in the life of the young universe when light first appeared. Holland Ford, an astronomer at Johns Hopkins University and the Godfather of Hubble science, calls it "this twilight zone between a universe that is illuminated by stars, galaxies and quasars, and the universe in that period before it that was dark, before there were stars and galaxies."

Hubble scientists face a big problem as they search for that light. They do not know exactly when it happened, even if they will still be able to see it. If it is too far away, the light may have shifted into the ultraviolet range, which means the search could have to wait for NASA's Next Generation Space Telescope, Hubble's successor, which is still in the design phase.

"This is why it's called the dark ages — we don't know," said Hubble astronomer Garth Illingworth. "This is one of the toughest problems we face: when did the stars and galaxies first turn on."

There is still the possibility that Hubble will startle us all with a very clear image of the first light. And that would be a neat trick for a telescope that most people were willing to write off as 25,000 lbs. of space junk with a warped mirror in the first years following its launch. That NASA was able to recover from that failure and give us the Hubble of today may be one of the space agency's greatest legacies.

Eventually, in one form or another, though, the Genesis image will reach us, and it is hard to say what the effect will be. Scientists have their own questions about the forces at work early in the universe and their relevance to the cosmos today, but the power of a photograph can have an impact broader than science. During Project Apollo, an astronaut took a picture of the frail, blue-and-white Earth rising above a desolate lunar landscape, and suddenly people realized just where they were. Some perspectives changed, and that photo helped take the environmental movement into the mainstream. So when the first rays of light have crossed the universe and reached our souls, who can say what they will illuminate?