What happens to a dark energy dream deferred?
An ambitious $1.6 billion spacecraft that would investigate the mysterious force that is apparently accelerating the expansion of the universe — and search out planets around other stars, to boot — might have to be postponed for a decade, the National Aeronautics and Space Administration (NASA) says, because of cost overruns and mismanagement on a separate project, the James Webb Space Telescope. The news has dismayed many American astronomers, who worry they will wind up playing second fiddle to their European counterparts in what they say is the deepest mystery in the universe.
“How many things can we do in our lifetime that will excite a generation of scientists?” asked Saul Perlmutter, an astronomer at the University of California, Berkeley, who is one of dark energy's discoverers. There is a sense, he said, “that we're starting to give up leadership in these important areas in fundamental physics.”
The satellite telescope
Last summer, after 10 years of debate and interagency wrangling, a prestigious committee from the National Academy of Sciences gave highest priority among big space projects in the coming decade to a satellite telescope that would take precise measure of dark energy, as it is known, and also look for planets beyond our solar system. The proposed project goes by the slightly unwieldy acronym Wfirst, for Wide-Field Infrared Survey Telescope.
The Academy's report was ambushed by NASA's announcement in November that the successor to the Hubble, the James Webb Space Telescope, which had been scheduled for a 2014 launching, would require at least another $1.6 billion and several more years to finish, pushing the next big mission to 2022 at the very earliest. The Webb will search out the first stars and galaxies to have formed in the universe, but is not designed for dark energy.
Euclid option
To take up the slack until 2025 — or whenever the American mission can finally fly — the space agency has proposed buying a 20 per cent share in a European dark-energy mission known as Euclid that could fly as soon as 2018. In return, NASA would ask for a similar investment by Europe in Wfirst.
But, said Dr. Perlmutter, “most of us think it is hard to imagine if we do Euclid now that we will do a dark-energy mission then.”
Alan P. Boss of the Carnegie Institution for Science, who heads a committee that advises NASA on astrophysics, said: “If Euclid goes ahead, they're going to own the field. There's no way the U.S. can stop them.”
Last month, the American astronomers' worries about falling behind seemed to be validated by a second Academy panel convened to consider the Euclid option. The panelists pointed out that part of the reason that Wfirst had been given such high priority was that it could be launched sooner rather than later. The panel urged NASA to stay the course or to explore merging Wfirst and Euclid in a joint operation.
Everybody agrees that nothing is cast in stone yet. Euclid must survive a bake-off with two other projects before it is approved by the European Space Agency, or E.S.A. Not until then, European astronomers say, will they be able to talk about changes to the project.
NASA has not said how it plans to get the $1.6 billion it needs to finish the Webb telescope, and thus how much will be left for other projects this decade. Some of the answers will be in the 2012 NASA budget due next month. “Fitting the E.S.A. and NASA processes together at this stage would be a challenge, but the scientific benefits are clear,” according to the new report by the Academy, which was delivered in December.
Jon Morse, director of astrophysics at NASA headquarters, said in an interview that NASA was committed to carrying out the recommendations of the original Academy survey that endorsed Wfirst. It is the “sense of Congress,” he said, that the Academy “should guide NASA science programmes.”
Asked about worries that Euclid could give the Europeans a big leg up in dark-energy work, Dr. Morse said, “The Europeans have developed a significant capability for doing their own missions.” “The scientific return for their investment has been outstanding,” Dr. Morse said, adding that European astronomers are looking for “frontier scientific discoveries” to make.
Dark energy a frontier science
Dark energy certainly counts as frontier science. The discovery a decade ago that the universe is speeding up, in defiance of common sense or cosmic gravity, has thrown into doubt notions about the fate of the universe and of life within it, not to mention gravity and even the nature of the laws of physics. It is as if, when you dropped your car keys, they shot up to the ceiling.
Physicists have one ready-made explanation for this behaviour, but it is a cure that many of them think is worse than the disease: a fudge factor invented by Einstein in 1917 called the cosmological constant. He suggested, and quantum theory has subsequently confirmed, that empty space could exert a repulsive force, blowing things apart. But the best calculations predict an effect 10 to the exponent of 120 times greater than what astronomers have measured, causing physicists to metaphorically tear their hair out and mutter about multiple universes.
In December, NASA solicited proposals from astronomers who want to join Euclid and named a team that will begin meeting in February to begin planning Wfirst.
One problem with Euclid from the Academy point of view is that it does not include observations of supernovae, the technique by which dark energy was discovered. Nor does the United States play a leadership role.
Dr. Boss, however, speaking personally, said he worried that those recommendations were out of date with new realities — budget and otherwise — and that following them could keep the United States out of what might be the only dark-energy mission for some time. “It's time for some creative thought,” he said.
“The European Union is producing more papers per year than the U.S.,” Dr. Boss went on. “They passed us a year ago and are doing quite well.”
Dr. Blandford, the chairman of the original Academy panel, agreed. “Dark energy and exoplanets are both fields of tremendous scientific importance and have caught the public's attention,” he said. “In both cases, the U.S. is currently the leading contributor. To abdicate that investment and opportunity would seem a terrible shame, but it doesn't mean we have to see Europeans as enemies we have to vanquish.”
Dr. Perlmutter, one of the discoverers of dark energy, sounded a similar note. “What's sad here is that everybody's been trying hard, there are no villains,” he said. “We all feel it is important to be at the table. At the end of the day we're scientists, you want to see science done.”— © New York Times News Service
