What will NASA’S biggest-ever space telescope study first?
Astronomers are scrambling to keep a rapidly approaching date with destiny — a chance to gaze farther than ever before into the Universe’s hidden depths.
After decades of development, the nearly $9-billion James Webb Space Telescope is set for launch from French Guiana in spring 2019. Built in cooperation with the European and Canadian space agencies, Webb is NASA’S biggest, costliest and most powerful observatory yet, boasting a 6.5-meter primary mirror that will be the largest ever flown in space, salon.com wrote.
Unlike its famous predecessor the Hubble Space Telescope, which mostly was set up to gather visible and ultraviolet light, Webb is optimized to view the cosmos in infrared. At some wavelengths, infrared light can pass through dust almost unscathed, like a sunbeam through a windowpane; at others, it mingles with matter to carry away imprints of its atomic and molecular structure. It is also the brightest light we have from the most distant (and oldest) stars because their otherwise-visible light arrives stretched out to longer, redder wavelengths by more than 13 billion years of the Universe’s expansion. Webb’s infrared eyes make it equal parts x-ray scanner, mass spectrometer and time machine. With them it will peer through the creaking, dusty cosmic eons to study much that astronomers using Hubble and other telescopes have barely begun to glimpse: The Universe’s very first galaxies, nascent stars and planets in mid-creation in nebulous wombs, the atmospheres of worlds both within and beyond our solar system.
Longevity is an even greater difference between Hubble and Webb. Thanks to a series of refurbishing missions to its post in low Earth orbit, Hubble is approaching its fourth decade of operations, a life span that has helped make it arguably the most productive and revolutionary scientific instrument in human history. Webb, however, will be stationed in deep space, past the orbit of the Moon, out of reach of easy servicing. It is intended to last at minimum five years — perhaps even 10, if all goes according to plan. For astronomers hoping to squeeze Hubble-like levels of discovery out of Webb’s limited life, every moment of the telescope’s time will be precious.
“Webb has a finite lifetime, and represents huge intellectual, financial and technological investments, so we need to hit the ground running to get its science flowing,” said Ken Sembach, director of the Space Telescope Science Institute (STSCI). “But there will be a steep learning curve. We want to make that curve as quick and easy to climb as possible.”
The hundreds of researchers who have spent decades developing the telescope’s hardware, software and core scientific objectives will be among the first to scale that learning curve. Each member of this elite cadre is guaranteed a small but significant portion of Webb’s total time, and much of the telescope’s first year of observations (called ‘Cycle 1’) is dedicated to fulfilling that obligation. Already intimate with what the telescope can do and given first picks of where to point it, these research teams are expected to generate some of Webb’s most transformative discoveries. Those initial results could then guide the rest of the world’s astronomers as they clamor to use Webb before it is gone. Except, that is, for rules hammered out early in the telescope’s development, which allow the researchers performing these ‘Guaranteed Time Observations’ to keep their results to themselves for a one-year period.
This delay “is an incredibly anachronistic concept, in the days of ‘big data,’ for an $8-billion mission funded with public resources with a five-year life,” said Garth Illingworth, an astronomer at the University of California, Santa Cruz, who also chaired an influential advisory committee for Webb. “The one-year proprietary period effectively means this hidden, unavailable data cannot be seen in time for follow-up by the community of astronomers until more than three years into [Webb’s] mission.” After unsuccessfully lobbying to change those rules, Illingworth instead helped create a new “Early Release Science” (ERS) program to circumvent them — up to 500 hours of diverse observations front-loaded to Cycle 1 for immediate release to the public, giving all astronomers a chance to absorb the results and apply lessons learned to Webb proposals of their own.
The precious hours for ERS would come directly from Sembach. As STSCI’S director, he commands 10 percent of Webb’s available time, and on November 13 he announced the final selections of 13 ERS proposals out of more than 100 from large research teams around the world. Each successful proposal will not only pursue novel science with Webb but also develop new tools and techniques for using the telescope that all astronomers can subsequently employ. “Getting these substantial programs in the public domain puts everyone on a more level playing field,” Sembach said. “Good ideas are what should dictate [Webb’s] observations going forward, not the past successes anyone happens to have.”
Illuminating the cosmic Dark Age
Astronomers have already begun leveraging Hubble and other space telescopes to create a preview of what Webb may reveal, staring at some of the largest galaxy clusters in a project called ‘Frontier Fields’. These clusters are so massive they warp the surrounding space, forming gigantic ‘gravitational lenses’ that amplify the faint light from galaxies even farther away, ones born less than a billion years after the big bang. Such galaxies are thought to be almost as old as any can be; for most of the Universe’s first half-billion years it languished in a cosmic ‘Dark Age’, too hot and dense for stars to form. But even through the galaxy cluster–size magnifying glass of a gravitational lens, Hubble can only see these early galaxies as dim smudges reddened by cosmic expansion. Webb — custom-built to study these murky epochs — could use gravitational lensing to unveil these and even older galaxies in sufficient detail and number to pin down exactly how these ancient objects arose and first brought light into the Universe.
One ERS program led by University of California, Los Angeles, astronomer Tommaso Treu will do just that, pointing Webb at a Frontier Fields cluster called Abell 2744 to see what lies beyond the limits of Hubble’s view. “With these observations we can look at everything from the very first galaxies to what we call the peak of star formation, a few billion years after the big bang, when galaxies are churning out stars and heavy elements at a crazy rate,” Treu said.