GMTO Welcomes New Community SAC Members
GMT welcomes Bob Blum (NOAO), Julianne Dalcanton (U. Washington) and Megan Donahue (Michigan State) to the Scientific Advisory Committee. They provide fresh perspective on key scientific issues, broaden participation from the larger community, and spread the word about progress with GMT outside the partner institutions. Their areas of interest include massive star formation, stellar populations in external galaxies, and x-ray studies of galaxy clusters.
Bob Blum is Deputy Director of the National Optical Astronomy Observatory. Bob’s research interests center on understanding the formation and evolution of massive stars. He is particularly focused on the galactic center and Magellanic Clouds. Dr. Blum received his Ph.D. from Ohio State University and served on the scientific staff at Cerro Tololo in Chile before moving to NOAO headquarters in Tucson. Bob has expertise in the development of instruments and observatory management in addition to his strong scientific credentials.
Julianne Dalcanton is Professor of Astronomy at the University of Washington and a renowned expert on stellar populations in external galaxies. Dr. Dalcanton received her Ph.D. at Princeton where she identified distant clusters of galaxies below the formal detection threshold of large area imaging surveys. She has led a number of large survey programs with the Hubble Space Telescope and is currently the principal investigator for a Hubble Treasury program to study resolved stellar populations in nearby galaxies. Julianne is actively engaged in the U.S. community through a number of high-level committees and authors a popular blog for Discover magazine:
Megan Donahue is Professor of Astronomy at Michigan State University. She is an expert on the study of clusters of galaxies and using x-ray and visible light instruments to study both the stars and hot atmospheres in galaxy clusters. Dr. Donahue received her Ph.D. from the University of Colorado and was a Carnegie Fellow in Pasadena. She was awarded the prestigious Trumpler Prize for her dissertation on intergalactic and intercluster gas. After completing her postdoctoral fellowship she became a member of the scientific staff at the Space Telescope Science Institute before joining the faculty at Michigan State. She brings expertise in large data archives as well as scientific perspectives to the GMT Science Advisory Committee.
First Annual GMT Community Science Meeting in Chicago June 10-12, 2013
Cosmology in the Era of Extremely Large Telescopes
The Giant Magellan Telescope Organization and the Kavli Institute for Cosmological Physics at the University of Chicago will host the first in a series of annual meetings to interface with the science community at large and engage scientists outside the GMTO consortium in thinking about the exciting opportunities that GMT and other new facilities will bring in the coming decade and beyond. The title of the 2013 meeting is “Cosmology in the Era of Extremely Large Telescopes.” The meeting will be held at the University of Chicago’s downtown Gleacher Center on June 10–12. Leading theorists and observers will discuss cutting edge research in cosmology and galaxy evolution and the role of large surveys and new facilities, including GMT, in enabling new discoveries.
The goal of the conference is to examine the role of galaxies as probes of cosmology, both today and in the future, as large galaxy surveys and the next generation of large ground-based and space-based telescopes come into being. We will bring together theorists and observers to discuss contemporary problems in cosmology and galaxy evolution as well as the opportunities offered by a new generation of facilities and surveys.
The conference will be organized into five half-day sessions. Keynote speakers invited from leading institutions around the world will provide an overview of the state of theory and observation in each subfield. Contributed lectures will delve into the details of front-line research issues. The first session will review relevant surveys and facilities, including the GMT, large imaging surveys such as the Dark Energy Survey, LSST and Euclid among others, plus upcoming missions such as the James Webb Space Telescope. This will be followed by sessions on First Light and Reionization of the Universe, Galaxy Formation and Assembly, Intergalactic and Circumgalactic Gas, and Galaxies and The Intergalactic Medium as probes of dark matter and dark energy.
The conference will be held in downtown Chicago at the University of Chicago’s Gleacher Center. A gala conference banquet will be held at the Adler Planetarium looking out onto Lake Michigan. Limited travel support is available for postdocs and students. It promises to be a fun and stimulating meeting.
Invited speakers include: Tom Abel (Stanford), Hsiao-Wen Chen (Chicago), Alan Dressler (Carnegie), James Dunlop (ROE), Joshua Frieman (KICP), Mike Gladders (Chicago), Marla Geha (Yale), Juna Kollmeier (Carnegie), Marc Postman (STScI), Risa Wechsler (Standford) and David Weinberg (Ohio State), among others. Please visit the conference website for more information: http://kicp-workshops.uchicago.edu/GMT_2013/
GMT Demonstrates Crucial Mirror Phasing Technique
Bringing the universe into focus
Imagine you built the biggest telescope in the world only to discover that its images were out of focus. It’s happened before. And historically, whenever a telescope has gotten bigger, the problems have gotten bigger too, something engineers call the “coefficient of difficulty.” In order for the GMT to achieve its optimal resolution, as much as 10 times that of the Hubble Space Telescope, there are two major challenges that must be conquered: blurring by the earth’s atmosphere and timing (or “phasing”) of the light from a distant object as it reaches each of the GMT’s mirror segments at slightly different intervals. The GMT team and scientists at the Smithsonian are excited with the results of a sophisticated new camera that addresses this phasing challenge.
The problem of our atmosphere
Even on a clear night when you can see the stars, our atmosphere is actually a turbulent swirling mess of air currents and temperature gradients caused by moisture evaporation, solar heating and the earth’s rotation. It’s what makes the stars twinkle, which may look pretty, but for astronomers it makes detailed study difficult. For the next generation of giant ground-based telescopes like GMT, engineers needed to correct for this problem. They will accomplish this with a system of computer controlled actuators called Adaptive Optics (AO) that will continuously, but very subtly, change the shape of the seven secondary mirrors, hundreds of times per second, with the assistance of laser guide stars to achieve clarity similar to space-based instruments. But that’s just the first part of the challenge.
Timing is everything
While the atmospheric blurring will been corrected with the GMTs sophisticated AO system, the wavelengths of light from extremely distant sources coming through the atmosphere will still hit the individual GMT mirror segments and finally the camera at the base of the telescope at slightly different times. Fixing that timing (or phasing) problem is essential to maintaining what astronomers call coherent light—an analogy being the difference between a turbulent confused sea and a calm sea with regular waves. Because very faint objects to be studied are so enormously far from earth, measuring and correcting these subtle time-of-arrival delays to the various mirror segments requires referencing light from actual stars in the Milky Way instead of an artificial laser-generated source. In addition to deforming the GMT’s adaptive secondary mirror with adaptive optics computers, a very precise type of camera to phase the incoming light from the secondary mirror will be also be essential.Dr. Brian McLeod and his team at the Smithsonian Astrophysical Observatory have designed and built a camera to demonstrate the phasing strategy for the GMT. The camera uses the faint light of an off-axis star to phase the telescope’s seven segments. The team tested their prototype Phasing Camera on the Magellan Clay Telescope at Las Campanas Observatory, the future home of GMT. By optically masking the Clay Telescope mirror to appear as if light were coming from two adjacent GMT mirror segments, they measured the accuracy with which the Phasing Camera can sense timing errors from the incoming light using stars of different magnitudes. The results confirm that the camera will be sufficiently sensitive to phase the telescope over at least 90% of the sky, allowing the GMT to achieve its promise of unprecedented resolution and usher in an exciting new era of cosmic exploration.
GMT Completes Most Challenging Mirror Ever Made
Scientists at the University of Arizona and the Giant Magellan Telescope Organization in California are celebrating a momentous achievement. On October 23, 2012 they announced that they have succeeded in completing the most challenging astronomical telescope mirror ever made. It is the first of seven mirrors that will operate together to form the 4000-square-foot light-collecting surface on the Giant Magellan Telescope. The scientists were particularly anxious about achieving the perfect shape for this first mirror because it is critical to the performance of the completed telescope and hence the success of the entire project. If they could succeed with this first mirror, they can succeed with the others.
Many aspects of polishing the giant mirror segment (27 feet in diameter) have never been attempted before.
Because the mirrors are designed to function together as one parabolic-shaped mirror, the six mirrors around the outer edge are asymmetrically shaped, or off-axis, a bit like a potato chip is curved. So the polishing head had to be specially designed to deform to match the curvature of the mirror exactly as it moved across the surface of the glass, polishing it to a precision of 1/20th of a wavelength of light. Put another way, the glass surface is so smooth that if the mirror were the size of the continental U.S., the highest mountains would be only about half an inch high.
The University of Arizona team designed, built and demonstrated all the equipment and techniques necessary for successful completion of all seven of the telescope mirrors. This first mirror blank was cast in a giant rotating furnace at the University’s famed Steward Observatory Mirror Lab beneath the football stadium. 20 tons of high-strength, low-expansion glass were melted into a mold in the oven and then spun at a high speed just right to achieve the initial parabolic shape, as you might twirl water around in a drinking glass. The formed glass was then slowly cooled for about three months before the mold was removed and grinding and polishing began.
The new mirror will remain at the Mirror Lab to be used as a reference mirror as the other mirrors are fabricated. The second mirror was cast in January 2012 and the third will be cast in August 2013. Subsequent mirrors will be cast in roughly 14-month intervals. When the Giant Magellan Telescope is completed near the end of this decade, it could well be the largest telescope in the world, with a light-collecting surface 80 feet in diameter (25 meters), roughly three times the diameter of the currently largest telescopes on Earth.
Located in the Andes at the foot of the great Atacama Desert in Chile, and with a resolution far greater than the Hubble Space Telescope, the GMT will have the potential to transform how we see the cosmos and our place in it, as it explores the universe back to the Big Bang and directly images earth-like planets around other stars.
GMT Instrument Science Workshop in Pasadena March 12-13, 2013 – Carnegie Observatories
GMTO and the GMTIFS instrument team will host a two-day workshop in Pasadena. The goal of the workshop is to inform the interested parties of the proposed capabilities of GMTIFS and the GMT laser and natural guide star AO systems. Participants will help generate a set of example science programs to aid in refinement of the instrument requirements. Information regarding the meeting and venue can be found at:
The meeting will be held at the Carnegie Observatories at 813 Santa Barbara St. and is open to all, subject to the capacity of the venue.