Celestial wish list

Astronomers prioritize projects for the coming decade

Astronomers tasked with compiling a priority list of U.S. astronomy projects for the next decade are seeing red, and not just because of NASA’s meager science budget. A National Research Council report released August 13 ranks several telescopes observing the universe at infrared and at even longer, redder wavelengths among the highest-priority instruments to be developed between 2012 and 2021.

These include the proposed Wide-Field Infrared Survey Explorer, an estimated $1.6-billion orbiting observatory that would examine the nature of dark energy, provide broad snapshots of the infrared sky and search for habitable, Earthlike planets. The telescope, which could be launched around 2020, would complement the ultrasharp but narrow vision of the James Webb Space Telescope, the infrared successor to the Hubble Space Telescope that is set to launch around 2015.

Infrared- and longer-wavelength telescopes enable astronomers to see farther away and thus further back in time, to the first stars, black holes and galaxies, fulfilling one of the overall goals set by the National Research Council panel. Chaired by astrophysicist Roger Blandford of Stanford University, the panel marks the sixth time that astronomers have come together to map the coming decade of U.S. astrophysics research projects.

But for the first time, this decadal survey includes independent appraisals of the technical readiness of missions, their cost and a development schedule. The committee also suggested that an independent panel be appointed to reappraise priorities in astrophysics more frequently, perhaps annually, as new technologies emerge and the risks associated with specific projects become clearer over the decade.

Given the burst of new technologies for ground-based and space missions, “I think we all wished we were back in the year 2000 trying to figure out how to spend a surplus,” rather than in the economically depressed era of 2010, says panel member Michael Turner of the University of Chicago. “I think we stopped whining after the first six months” and tried to emphasize international and private partnerships for funding missions, he adds.

The panel recommended that the United States continue with plans to develop the Laser Interferometer Space Antenna, an array of low-frequency detectors that would aim to detect gravitational waves — ripples in spacetime generated by distant black hole mergers and the motions of closely orbiting, dense stars within the Milky Way. The estimated $2.4 billion mission might be ready in 2025, but should go forward only if a test mission meets with success, the panel concluded.

Most of the proposed projects — both in space and on the ground — selected by the panel would not be ready until the 2020s, Turner says.

In addition, the committee highly ranked two other newly proposed space missions — the International X-ray Observatory, which would examine the hot gas around stars and galaxies, and a probe to further study the early epoch of expansion known as inflation and the cosmic microwave background, the whisper of radiation left over from the Big Bang. The mission would be a follow-up to the European Space Agency’s Planck mission, launched in 2009.

One mission that failed to make the cut was the SIM Lite Astrometric Observatory, designed to survey some 40 nearby stars for Earthlike, habitable planets. Although the proposed mission has mastered all technological obstacles and could be launched relatively quickly, the panel decided that the money would be better spent on the development of missions that could survey a much larger number of stars and lay the groundwork for imaging Earthlike planets, Turner says. 

Among large-scale, ground-based projects, the panel ranked highest the $465 million Large Synoptic Survey Telescope, a wide-field visible-light telescope that would observe more than half the sky every four nights, search for supernovas and probe the nature of dark energy by examining how the shapes of galaxies are distorted over cosmic time.

Blandford and his colleagues also recommended a federal contribution of 25 percent to the roughly $1.4 billion International Giant Segmented Mirror Telescope, an endeavor geared to building one of the largest visible-light and infrared telescopes ever constructed.

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