The James Webb Space Telescope, NASA's next flagship telescope slated to become the largest telescope ever launched to space, recently emerged from Chamber A, a massive cryogenic testing chamber at NASA’s Johnson Space Center. James Webb and its 6.5-meter primary mirror were sealed in the chamber for more than four months of operational testing in space-like conditions.
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The nearly $9-billion telescope built in partnership with the European and Canadian space agencies is in good shape, but there is a long way to go before Webb is ready to strap to the top of an Ariane 5 rocket and blast off. The space telescope's launch was recently pushed back from October 2018 to sometime between March and June of 2019, and further delays are possible. The spacecraft that will carry the telescope and keep it in the proper orbit, which includes a spacecraft bus and a large sunshield, is taking longer to manufacture than expected.
However, NASA is by no means attempting to rush the final stages of James Webb's development. An independent review in January will determine the status of the space telescope and NASA will announce a new planned launch date following the review in late January or early February. “At this stage in the project, a few extra days or weeks or even months of schedule delay, or the expenditure of some additional dollars, is a small price to pay to ensure success of a mission as important as JWST," said retired aerospace executive Thomas Young while testifying before the House Science Committee’s space subcommittee on December 6, as reported by Space News.
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In the meantime, science teams are eagerly planning the first targets for the powerful new space telescope. Unlike the Hubble Space Telescope, which takes observations in mostly visible and ultraviolet light, James Webb will take observations in mostly infrared wavelengths. Infrared is particularly useful to astronomers studying the early history of the universe, as visible light from objects 13 billion light-years away stretches and redshifts into the infrared part of the spectrum by the time it reaches Earth. Infrared light is also useful for peering through clouds of space dust and for spotting exoplanets around their host stars, as detecting a planet's heat signature in infrared can be easier than spotting it in visible light.
James Webb's mission is slated to last a minimum of five or ten years, but after that, it's possible that observations with the space telescope will no longer be viable. Hubble was serviced by astronauts multiple times and has been operational for almost 30 years as a result. James Webb, on the other hand, will park in an orbit much farther away, beyond the moon, so sending astronauts to repair or service the telescope once it deploys will likely be impossible. Everything needs to go right, and once Webb is up and running, the clock for science will start ticking immediately.
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The researchers and scientists who helped design and build the James Webb Space Telescope will get first dibs on what to point it at. The first year of operations, known as Cycle 1, is primarily devoted to fulfilling these "Guaranteed Time Observations," according to Scientific American.
A policy ironed out early in the telescope's development phase allows these first researchers who use the telescope to keep their results confidential for up to one year. Many in the scientific community deplore the policy, as the data from early observations could be vital to determining future studies for James Webb's relatively short lifetime.
The policy “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,” Garth Illingworth, an astronomer at the University of California, Santa Cruz, who chaired an advisory committee for Webb, told Scientific American. “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.”
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Illingworth has unsuccessfully lobbied to change the rules, although he and other scientists have found a way to partially get around them. The UC Santa Cruz astronomer helped launch what is known as the "Early Release Science” (ERS) program, which carves out time during Cycle 1 for up to 500 hours of telescope observations that will be immediately released to the public. Access to this early data, argues Illingworth, is vital to allow astronomers the information they need to draft their own science proposals for the Webb telescope.
Out of more than 100 ERS proposals, the Space Telescope Science Institute (STScI) has selected 13. The early science with James Webb broadly focuses on three categories: early galaxy and star formation, exoplanet atmosphere studies, and the watery worlds of our own solar system.
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Recently, two major studies about some of the farthest and oldest galaxies in the universe were published. More than 13 billion light-years away and therefore 13 billion years ago, these galaxies formed in the Epoch of Reionization just after the Dark Ages of the universe, when conditions were too hot and dense for stars or galaxies to form. Exactly when the first stars burst into life, and how they formed the first galaxies, is one of the greatest mysteries in cosmology. Webb should be able to find older galaxies than ever before, and tell us roughly how many formed in the first billion years after the Big Bang.
Exoplanets are one of the most exciting topics in astronomy right now, and James Webb is destined to teach us even more about these planets that orbit beyond our solar system. With its sensitive infrared instruments, James Webb should be able to determine the atmospheric composition of larger exoplanets based on the the starlight passing through, some of which will be blocked by various chemical elements. Measuring the distribution of molecules in an exoplanet's atmosphere, such as molecular oxygen, methane and carbon dioxide, is the first step to determining whether that planet might be able to support life. Among the first exoplanets James Webb will observe, however, are the Jupiter-sized gas giants WASP-39 b and WASP-43 b.
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Finally, James Webb will also be used early on to take a look at some worlds closer to home, specifically Jupiter's moon Europa. The fourth-largest moon of Jupiter is thought to eject icy material from a subsurface ocean out into space, and James Webb will use is large mirror and powerful instruments to attempt to confirm the presence of geysers and plumes on Europa. The telescope could be vital to providing data for the upcoming Europa Clipper mission, scheduled to launch in the early 2020s, which will perform several flybys of the watery moon to search for signs of life.
From the earliest stars and galaxies of the cosmos, to the tantalizing watery moons on our front doorstep, James Webb will have no shortage of work. Though additional delays and costs are possible, the stages of the mission leading up to launch are in many ways the most crucial. We only have one shot to get this right, and if we do, the results will be spectacular.
h/t Space News and Scientific American
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