Astronomers’ hopes of studying dark energy fade
A star-crossed mission nearly 20 years in the making intended to seek an answer to the most burning, baffling question in astronomy — and perhaps elucidate the fate of the universe — is in danger of being canceled.
The Wide-Field Infrared Survey Telescope, or WFIRST, was being designed to investigate the mysterious force dubbed dark energy that is speeding up the expansion of the universe and search out planets around other stars.
In 2010, a blue-ribbon panel from the National Academy of Sciences charged with charting the future of space-based astronomy gave the mission the highest priority for the next decade. Under the plan, it could have launched in mid-2020s with a price tag of $3.2 billion.
But it was zeroed out in the NASA budget proposed by President Donald Trump last week.
In a statement accompanying the budget, Robert M. Lightfoot Jr., the agency’s acting administrator, called the deletion “one hard decision,” citing the need to divert resources to “other agency priorities.” NASA is shifting its focus back to the moon.
Nobody is under any illusion that a president’s budget proposal is the last word on anything. Congress, which usually listens to the academy’s recommendations, will have the last word
The proposed cancellation drew an outcry from astronomers, who warned stepping back from the mission would be stepping back from the kind of science that made America great and would endanger future projects that, like this one, require international help. It drew comparisons to the cancellation of the Superconducting Supercollider that ended U.S. supremacy in particle physics.
David Spergel, former chairman of the academy’s Space Study Board, noted that in planning their own programs, other countries depended on the United States to follow the advice of the National Academy.
Astronomers have hungered for a space mission to investigate dark energy ever since 1998, when observations of the exploding stars known as supernovae indicated the expansion of the universe was speeding up, the distant galaxies were shooting away faster and faster from us as cosmic time went on. It is as if, when you dropped your car keys, they shot up to the ceiling.
The discovery won three American astronomers the Nobel Prize. The fate of the universe, as well as the nature of physics, scientists say, depends on the nature of this dark energy.
Physicists have one ready-made explanation for this behavior, but it is a cure 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 subsequently has confirmed, that empty space could exert a repulsive force, an anti-gravity, blowing things apart.
If so, as the universe grows, it will expand faster and faster and run away from itself. Eventually other galaxies would be flying away so fast we couldn’t see them. The universe would become dark and cold. Cosmologist Lawrence Krauss of Arizona State once described this as “the worst possible universe.”
If on the other hand, some previously unsuspected force field is tinkering with the galaxies and space-time, the effect could shut off or even reverse over the eons.
Or maybe we just don’t understand gravity.
Dark energy, said Frank Wilczek, a Nobel laureate from the Massachusetts Institute of Technology, “is the most mysterious fact in all of physical science, the fact with the greatest potential to rock the foundations.”
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 also can gauge dark energy by how it retards the growth of galaxies and other structures in the universe.
In 1999, Saul Perlmutter of the Lawrence Berkeley Laboratory, one of dark energy’s discoverers, proposed a space mission known as SNAP (Supernova Acceleration Probe) to do just that.
In 2008, NASA and the Energy Department budgeted $600 million, not including launching costs, for a mission and the call went out for proposals.
In 2010, a committee of the National Academy of Sciences cobbled together several competing proposals that would do the trick. Paul Schechter, an MIT astronomer involved in the work called it WFIRST, for Wide Field Infrared Survey Telescope. But the telescope also would search for exoplanets — planets beyond our solar system.
In its report, “New Worlds, New Horizons,” the committee gave this mission the highest priority in space science for the next decade.
But NASA would have no money to start on this project until it finished building the James Webb Space Telescope, the successor to the vaunted Hubble Space Telescope. Shortly after the academy’s deliberations, the space agency admitted the Webb project had been mismanaged. The telescope, which had been set for a 2014 launching, would require at least another $1.6 billion and several more years to finish. The Webb will search out the first stars and galaxies to have formed in the universe but is not designed for dark energy. It is now on course to be launched next year.
WFIRST would have to wait.
The ball is now in Congress’s court.