National report on space program recommends missions to study dark energy and black holes

Joel Primack

UCSC physics professor Joel Primack had some good news for his colleagues when he gave a briefing on campus last week to outline the findings of a national report on NASA's space science programs. Primack is the senior cosmologist on the National Research Council (NRC) committee that issued the report, which recommends pursuing at least two ambitious space missions that should yield extraordinary results for astrophysics researchers at UCSC and around the world.

"These missions address key questions that will take science beyond the achievements of the Einstein century," Primack said.

The recommendations include a mission to investigate dark energy and the expansion of the universe, and another to explore black holes and gravity waves. These are among the most exciting areas of current cosmological research, Primack said.

NASA's "Beyond Einstein" program originally had outlined a robust astrophysics program involving numerous space missions, all of which were indefinitely postponed in 2004 when President Bush announced a new "Vision for Space Exploration." The Bush plan made NASA's top priority to put astronauts back on the Moon and eventually send them to Mars, but scientists were disappointed to see funding for science missions cut. NASA's decision to cancel a mission to repair the Hubble Space Telescope caused such an outcry, not only among scientists but also from the general public, that it was eventually reversed.

In 2004, Primack chaired a panel of the American Physical Society that issued a report on the Bush Administration's Moon-Mars program, predicting it would have dire effects on U.S. space-based astronomy.

"I am hopeful that the NRC Beyond Einstein report will help the U.S. restart our promising programs for exploration of the universe," he said.

Other UCSC faculty have also been at the forefront of efforts to restore funding for space-science programs. Professor of astronomy and astrophysics Garth Illingworth, for example, who chairs the congressionally chartered Astronomy and Astrophysics Advisory Committee, testified before Congress in May about the effects of budget cutbacks on NASA's science program (see earlier story).

The NRC committee, established under pressure from Congress, was charged with reassessing NASA's Beyond Einstein program and recommending which of the program's five proposed mission areas should be developed and launched first.

The committee gave first priority to the Joint Dark Energy Mission (JDEM), a joint program of NASA and the U.S. Department of Energy to measure how the universe's expansion rate has changed over time. In 1998, scientists studying supernovae discovered that the expansion of the universe is accelerating. This led to the idea of dark energy, a mysterious force that permeates the universe and drives its rate of expansion. But dark energy remains one of the most puzzling concepts in modern cosmology.

Three groups are working on proposals for the JDEM mission, and NASA will choose which proposal to fund. All three proposals aim to precisely measure the expansion history of the universe to determine whether the contribution of dark energy to the expansion rate varies with time.

The committee's second priority is the Laser Interferometer Space Antenna (LISA), a mission that has been in development for some 20 years. Its primary objective is to detect gravitational waves, ripples in space-time caused by the movement of massive bodies such as black holes. These waves are predicted by Einstein's theory of general relativity, but have yet to be directly detected. LISA would be used to study the mergers of supermassive black holes and to probe the early universe. According to Primack, NRC committee members estimated that three Nobel Prizes could ultimately be awarded on the basis of results from the LISA mission.

Although implementation of NASA's Beyond Einstein Progam has been delayed, Primack said the committee has recommended that all of the original missions still be supported and considered for eventual implementation.

"All of the mission areas in the Beyond Einstein program have the potential to fundamentally alter our understanding of the universe," said committee co-chair Charles F. Kennel of UC San Diego. "But JDEM will provide direct insight into a key Beyond Einstein science question and is the most technically feasible option for immediate development."