Quest for Dark Energy May Fade to Black

By DENNIS OVERBYE Published in New York Times: January 3, 2011

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, 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.”

 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.

To take up the slack until 2025 — or whenever the American mission can finally fly — the space agency has proposed buying a 20 percent 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 programs.”

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 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 behavior, 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.

The astronomers who made this discovery were using the exploding stars known as Type 1a supernovae as cosmic distance markers to track the expansion rate of the universe.

Since then, other tools have emerged by which astronomers can also gauge dark energy by how it retards the growth of galaxies and other structures in the universe. So far the observations are consistent with it being Einstein’s constant, but not definitive; more precise measurements, many of which can only be done from space, are needed.

Dr. Perlmutter, who works in the Department of Energy’s Lawrence Berkeley National Laboratory, proposed a dark energy mission known as SNAP (Supernova Acceleration Probe) in 1999. In 2003, the White House asked the Energy Department to partner with NASA on the project, which became known as JDEM, for Joint Dark Energy Mission, and a call went out for competing proposals.

But NASA and the Energy Department found it hard to collaborate, and several rounds of meetings and committees went nowhere. “Maybe we shouldn’t have tried to ride two horses,” Dr. Perlmutter said.

In 2008, NASA and the Energy Department budgeted $600 million, not including launching costs, for a mission, but a working group of dark-energy scientists could not come up with a design that would fit in the budget.

Feeling that the blessing of the National Academy of Sciences was needed to proceed with a more expensive project, Dr. Morse submitted a couple of versions of the dark energy mission to the Academy panel — also known as Astro2010 — that was charged with setting priorities for the astronomical community for the next decade.

Alan Dressler of the Carnegie Observatories, who led one of the panel’s subcommittees, noticed that three of the submitted projects — including dark energy, a search for planets around other stars, dubbed exoplanets, and a survey of infrared radiation from the heavens — all required the same hardware. He proposed combining them into a larger mission (“putting more eggs into the basket,” in Dr. Perlmutter’s words), in a project that could launch around 2020. That larger mission they dubbed Wfirst.

“It looked then and it still looks to me like a good deal,” said Roger Blandford of Stanford, an astrophysicist and the chairman of the Astro2010 panel.

Meanwhile, the European Space Agency had also made dark energy a priority. Last February, the Europeans sent NASA a letter offering the Americans a 20 percent piece of Euclid and two slots on the mission’s science team. American astronomers were ambivalent. Joining Euclid would divert resources from their own mission, thus delaying it.

In September NASA’s advisory committee on astrophysics, which is led by Dr. Boss of the Carnegie Institution, concluded that Euclid could spend three or four years “skimming the cream off the dark energy pail” before Wfirst got into the sky.

Both Dr. Boss’s council and yet another committee, the Astronomy and Astrophysics Advisory Committee, which counsels the National Science Foundation and Energy Department as well as NASA, concluded that joining Euclid was not in keeping with the original Academy recommendations.

By the time the second Academy panel reported in December, the news about the Webb telescope’s problems had made everything worse. The Webb, which was the highest Academy priority 10 years ago and has already cost $5 billion, could not be launched any earlier than 2015 and would probably be even later, because of NASA’s inability to correctly estimate how long it would take to do things like test the telescope. How much of the $2.2 billion that NASA was to have available for new astrophysics missions this decade will be left once Webb is taken care of is anybody’s guess.

On top of that, NASA faces what Dr. Morse calls “an evolved difficult fiscal environment,” with Republicans bent on reducing the federal budget taking over the House of Representatives.

Some astronomers said they felt ambushed by NASA and Dr. Morse, who briefed the Astro2010 panel during its two years of deliberations. “He didn’t know? He should be fired,” said Dr. Dressler of the Carnegie Observatories.

Dr. Morse said he understood and shared his colleagues’ frustration. But said he had warned the panel all along that its plans could be upset by the Webb, which has always been known to have problems. “The community,” he said, referring to the Astro2010 panel, “did the best job they could with what they were given. The fiscal constraints are far worse now than we could imagine a year ago.”

Or, as Michael Turner, a cosmologist at the University of Chicago and a member of Astro2010, put it, “We’re in a terrible mess.”

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.”

This entry was posted in Nature and tagged , , , , , , , , . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s