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James Webb Space Telescope (JWST), NASA

UA Astronomers Anticipate Launch of James Webb Space Telescope

As the launch, deployment, and operation of JWST approaches, this website will keep you informed of the UArizona presence and scientific work on JWST. We intend to carve out a permanent space on this front page for JWST and other major-mission events in the Dept of Astronomy and Steward Observatory.

For now, while we make some website changes, we'll list UArizona JWST papers and press relases here, at the top of this webpage. Here is the first one:


There is a new website dedicated to JWST at UArizona. Feel free to visit it often.

The James Webb Space Telescope is finally, after twenty years of study, development, and ten billion dollars of investment, ready to ship to its launch site, on the brink of going into space.  The University of Arizona has been central in this twenty-year journey, a role that is reflected in the award of 1332 hours (13%) of the observing time in the first year of operation, time that was hotly competed for throughout the astronomical community around the world.

The Webb Telescope will be launched on an Ariane 5 from French Guiana, but its full aperture of 6.5 meters, or 21 feet, is too large to fit inside the fairing of even this huge rocket. Instead, it is launched folded up and unfolds only when it is in space, where its optics are aligned to make good images. Once unfolded, it cools to -420 degrees Fahrenheit, so its warmth does not blind its sensitive infrared – heat wave – detectors. While all this is happening, it coasts to a “Lagrangian point,” four times further away than the moon, where it can formation fly with the earth around the sun, and from where it sends its data back to Earth from a distance of a million miles. The gains over the most powerful previous space infrared telescope, the Spitzer Space Telescope, are nearly 100 times in sensitivity, nearly 100 times in angular resolution element, and, with modern arrays of infrared detectors, more than 100 times in number of pixels.

Making full use of such an advance might boggle astronomers’ imaginations.  But not for our local astronomers, who saw the potential to make huge leaps in understanding scientific puzzles they had pursued for years, ranging from the formation of supermassive black holes and emergence of the first galaxies in the universe, to the growth of young stars and the properties of exoplanets resembling our own Solar System. Early-on, they won contracts to lead the construction of the Near Infrared Camera (NIRCam) under Professor Marcia Rieke, and as Science Team Lead for the Mid-Infrared Instrument (MIRI) under Professor George Rieke.

Many other local astronomers have successfully competed for observing time to pursue life-long goals. For example, Professor Xiaohui Fan discovered quasars (supermassive black holes glowing brightly as matter falls into them) at the edge of the Universe when he was a graduate student more than two decades ago. Along with Drs. Jinyi Yang, Feige Wang, and scientists at other institutions, he will use JWST to study the most distant known examples, three quasars so far away that the cosmic redshift has put all of their light into the infrared where JWST is needed to study it in detail. An astronomical conundrum is how the black holes powering these quasars could have grown so fast, to reach a billion times the mass of the sun just 700 Million years after the Big Bang. This program will measure masses of these three quasars, probably to set a new record for the required rate of black hole growth. How these distant quasars grow and whether they actually lie in massive galaxies as is the case for all local quasars is the topic of two other programs that are centerpieces for the local MIRI program. Jianwei Lyu, Stacey Alberts, and George Rieke will survey the region of sky with the deepest X-ray, radio, and optical maps to see if any quasars have still been able to hide there, for example behind dense clouds of dust. They will also image some of the most distant quasars to see if they can finally spot galaxies around them. C.K. Chan is leading a program to determine how the massive black hole in the center of our Milky Way operates. Yang, Wang, Fan, and collaborators will also use distant quasars as light beacons, studying how the character of their light is modified as it passes through galaxies and intergalactic material on the way to us. This is a unique way to learn about material that is not glowing brightly enough to observe it directly.

Quasars loudly call attention to themselves since they glow so brightly they can be readily spotted across the entire Universe. Young galaxies are a much bigger challenge to find, and finding them was the initial rationale for building the Webb telescope. The NIRCam team has put together a major program co-led by Drs. Kevin Hainline, Eiichi Egami, Christina Williams, Marcia Rieke, and others, that combines some of their time with that of the NIRSpec team (based in Europe). Together, they will use 800 hours of observations to conduct a huge program of surveying apparently empty sky to find the first galaxies. In this case, “empty” means free of nearby stuff that would block our view. This approach was pioneered by former UA professor Bob Williams when he was the director of the Space Telescope Science Institute, and his initiative led to the establishment of the by-now famous Hubble Deep Field. As with the very distant quasars, the Universal redshift has caused the light of the very youngest galaxies to shift so far to the infrared that they cannot be studied well with HST, but Webb will open a vista into their properties. Dr. Christina Williams is leading another search for these galaxies, in this case observing “for free” at empty sky made available while other astronomers point Webb at some specific target they want to study. The behavior of these early galaxies may differ significantly from nearby ones because they have not had time to build up elements heavier than hydrogen and helium as stars evolve, explode, and throw off material. Such “trace” materials, although just a tiny part of the total mass of gas, regulate how the gas is heated, how energy is passed from the cores of stars to their surfaces, and in general regulate the properties of most astronomical objects. These effects will be studied with Webb by Dr. Irene Shivaei and Professor Dan Stark, as part of two distinct programs.

Warm dust around forming stars and at the temperatures typical of the outer Solar System was discovered by our late Research Professor Frank Low and his then postdoc Doug Kleinmann (in 1968). We now know that this dust is the signature of disks of gas and dust much of which is accreting onto the star and making it grow, but also where planets are forming. This behavior was studied extensively by Steve and Karen Strom at Kitt Peak.  Now Professor Ilaria Pascucci of our Planetary Sciences Department will use JWST to investigate how magnetic fields control the accretion and thus the growth of the star, and also to investigate cases where the disk seems to have opened up holes possibly as planets formed. Young stars also blast the surrounding gas and dust with their ultraviolet radiation. The results will be evaluated by Karl Misselt and others as part of the NIRCam program.

Much of the news generated by astronomers over the last 25 years has centered on the discovery of planets orbiting nearby stars, definitely implying but not yet proving that we are unlikely to be alone. This area has not been ignored by our local astronomers. Webb provides a great advance in sensitivity at the premier spectral region to image new planets, an enterprise that has proven difficult with existing telescopes and instruments. The NIRCam team will obtain images to search for planets, particularly around nearby, young, and low mass stars where they will have a hard time hiding if indeed they are there. The team will also look at the nearest stars with massive planetary systems as revealed by clouds of dust when members of these systems collide and smash each other up, in a program led by Drs. Andras Gaspar, Schuyler Wolff, Kate Su, and Jarron Leisenring. To achieve an objective that seemed impossible when exoplanets were first discovered, Arizona NIRCam team members Drs. Everett Schlawin, Tom Beatty and former Arizona graduate student Tom Greene (now at NASA Ames) are leading a program to take spectra of the members of other planetary systems, observations that will reveal the state of the gases in their atmospheres. This is done by taking spectra of the star plus planet as the planet passes in front of its star, then carefully computing the spectrum of the change in light from the combined system. Finally, when is a planet not a planet? The answer is when it escapes from its star and floats free in space. The NIRCam team will survey for these escaped former planets in a program led by former astronomy faculty member Mike Meyer (now at the U of Michigan).

All of this frontline science depends on getting the telescope successfully into space. After twenty years of designing, building, and testing, the Webb Telescope and spacecraft are about to be shipped to the launch site in French Guiana. From there, they will be lofted into space on top of the Ariane 5. The launch itself will be a time of great nervousness for astronomers worldwide; all the work in building Webb could go up in a giant puff of smoke.  Moreover, as Thomas Zurbuchen,  NASA Associate Administrator for Space Sciences, points out: “It will take about three weeks to deploy Webb, and scientists will be on edge the entire time. Those who are not worried or even terrified about this are not understanding what we are trying to do.” We do not generally think of scientists as being superstitious. However, astronomers will indeed have fingers crossed, rabbits’ feet firmly in hand, and invocations dutifully chanted until Webb is out to its final location and starts returning the observations it has been promising them for twenty years.

We thank Regents' Professor George Rieke for this article.

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