May 11, 2009|By Frank D. Roylance | Frank D. Roylance,frank.roylance@baltsun.com
The picture on Adam Riess' computer monitor arrived fresh from the orbiting Hubble Space Telescope. It was the fading light from an exploding star, potentially a key piece of evidence in his yearslong investigation of one of the greatest of all cosmological mysteries - dark energy.
But as the Johns Hopkins University astrophysicist waited for the next image to arrive, an e-mail message popped onto his screen. In an instant, he tumbled into what he describes as one of those "uh-oh" moments when everything changes.
Hubble's Advanced Camera for Surveys - or the part of it vital to his research - had shut itself down. And it was quickly apparent that it would not come back. Riess' work on the scientific puzzle that had made him famous was finished, maybe for years. Maybe forever.
That was more than two years ago, and Riess is one of hundreds of Marylanders whose jobs and passions will be riding on space shuttle Atlantis as astronauts attempt a grueling series of five spacewalks to upgrade and repair the famed Hubble telescope.
The three-day launch window opens Monday at 2:01 p.m. for Atlantis and its seven-member crew as they set out from Cape Canaveral to extend the life of history's most productive observatory by at least another five years, add two new, more powerful instruments and restore life to two others, including ACS.
But it would be hard to find anyone with more at stake than Riess.
He was just 29 years old in 1998 when he became the lead author on the first dark energy paper to be published. It turned out to be one of the most momentous discoveries in cosmology. Ever.
He and his team had used a peculiar class of exploding star, called Type Ia supernovae, as mile markers across the universe. By measuring each stars' brightness, they could calculate their distances. And by analyzing their light spectra, they could measure how fast the universe was expanding when the light left each star. By plotting that expansion rate over time, they discovered that the cosmos has been expanding at an accelerating rate for billions of years.
The discovery (also made independently by another team) was astonishing, as if his paper had reported they tossed a brick into the air and watched it zoom into space, instead of falling back to Earth. Gravity was supposed to slow the universe's expansion over time, not accelerate it. The unexplained force driving that acceleration was dubbed "dark energy."
"It appears to make up about 70 percent of the mass/energy budget of the universe," he said. "But that's about all we know. It's very mysterious, and we're quite desperate to understand what it is, how it operates, and what its physics is."
Riess' paper has become one of the most cited in the cosmology literature. It has earned him and his colleagues a share of some of the richest and most prestigious awards in science, including the Peter Gruber Prize in Cosmology in 2007, and the Shaw Prize in 2006.
In September, he was named a MacArthur Fellow, accepting a $500,000 no-strings grant in recognition of his groundbreaking work. Last month he was elected to the National Academies of Science.
With enough data from as many Type Ia supernovae as he can find, Riess still hopes to unravel the mystery of dark energy. By 2007 he'd found 25 at least 9 billion light years away.
Riess has continued with related work that last week provided more precise estimates of the expansion rate of the universe, an advance that is expected to help scientists test theories about dark energy.
But the ACS was the only instrument anywhere today with the sensitivity and the wide field of view capable of quickly and efficiently cataloging Type Ia supernovae at vast distances before they fade away.
Atlantis astronauts will be installing a new Hubble instrument - the Wide Field Camera 3 - but it's only half as efficient as ACS at this work.
More and better tools may be coming. "It's a very hot topic right now. NASA and the Department of Energy are in the process of planning what could become a billion-dollar space mission to study dark energy," Riess said. But for now, "the Hubble Space Telescope and ACS are the only game in town, and may be so for the next 15 years."
When that fateful e-mail flashed on his screen in 2007 saying that ACS was gone, Riess' work skidded to a halt.
"Space science is not for the faint of heart, or those who demand continual gratification," he said.
Still, it is a seductive quest, not easily abandoned. It's as if humans had always lived far inland, and suddenly ventured out and discovered the oceans, which cover two-thirds of the planet, Riess said. "We'd go, 'Wow! What is this?' And we'd spend a lot of time studying the oceans and what their significance is."
