Keck Observatory Astronomer Wins Top Award

Keck Observatory Astronomer Wins Top Award

Credit: Andrea Ghez

Dr. Andrea Ghez

Keck Observatory Astronomer Wins Top Award

Credit: Keck/UCLA Galactic Center Group

The orbits of stars within the central 1.0 X 1.0 arcseconds of our Galaxy. In the background, the central portion of a diffraction-limited image taken in 2010 is displayed. While every star in this image has been seen to move over the past 15 years, estimates of orbital parameters are only possible for the seven stars that have had significant curvature detected. The annual average positions for these seven stars are plotted as colored dots, which have increasing color saturation with time. Also plotted are the best fitting simultaneous orbital solutions. These orbits provide the best evidence yet for a supermassive black hole, which has a mass of 4.1 million times the mass of the Sun.

A Keck Observatory astronomer who led the way to the discovery of a super-massive black hole at the center of our galaxy has been recognized this week with the 2012 Crafoord Prize in Astronomy, an award almost as prestigious for astronomers as a Nobel Prize.

“This is a big one. I’m thrilled,” said Andrea Ghez of the University of California at Los Angeles. For more than 16 years Ghez and her team have been pushing the frontiers of high-resolution imaging technologies with the twin 10-meter Keck telescopes in order to explore the center of the Milky Way. By tracking the rapid, small-scale orbits of stars at the Galactic Center, they discovered the presence of a source of tremendous gravity – the best evidence yet that a supermassive black hole exists there. The reality of such an object confronts and challenges our knowledge of fundamental physics.

Ghez , who holds UCLA’s Lauren B. Leichtman & Arthur E. Levine Chair in Astrophysics and heads UCLA’s Galactic Center Group, will be sharing the prize, and its 4 million Swedish Krona or $600,000 award, with Reinhard Genzel, scientific director of Max-Planck-Institute for Extraterrestrial Physics in Garching, Germany. Genzel leads a group that has long worked independently to track the same stars at the Galactic Center. 

“This year´s Crafoord Prize Laureates have found the most reliable evidence to date that super-massive black holes really exist,” reads a Jan. 19 release from the Royal Swedish Academy of Sciences. “For decades Reinhard Genzel and Andrea Ghez, with their research teams, have tracked stars around the center of the Milky Way galaxy. Separately, they both arrived at the same conclusion: in our home galaxy resides a giant black hole, called Sagittarius A.” 

Ghez, born in New York City and raised in Chicago, started the project in 1995, when she was a fresh new assistant professor at UCLA, looking for a project that would make good use of her talents in high-resolution imaging.

“I had no idea that this project would lead to such recognition” Ghez laughed. “I was a new assistant professor and I was just looking for tenure. It was my very first Keck proposal.”

Her proposal was accepted and she went to work showing how a technique called speckle imaging could be used to dramatically sharpen images using what was at the time the world’s only 10-meter optical-infrared telescope: Keck I. Speckle imaging corrects for the blurring effects of the earth’s atmosphere in processing of images after they have been captured by the telescopes’ instruments. These allowed the first diffraction-limited images – that is, images that are limited by a telescope’s power rather than the Earth’s turbulent atmosphere – to be produced with these large ground-based telescopes.

“I wanted to show that speckle worked at Keck,” Ghez said. It did and it produced the first images that had the full resolving power of the Keck telescope. But that was just a start. By 1999 the Keck II telescope was also operating and had become the first large telescope in the world to employ adaptive optics, a technology that cancels out distortions in starlight created by turbulence in Earth’s atmosphere. That sharpened the images of the Galactic Center ten-fold and allowed diffraction-limited spectroscopic measurements to be made for the first time.

“It’s been like riding this incredible wave of technology,” Ghez said. “Since 1995 we have spent time at the telescopes every summer working on this. I had no idea what a rich project I was getting into at first. While the initial question was ‘is there a supermassive black hole at the center of our galaxy’, we have uncovered so many unexpected phenomena and technology has moved so fast that we created more questions than we answered”

“This research was possible thanks to the W. M. Keck Observatory, which houses the two largest telescopes in the world,” said Ghez. “They have enabled us to achieve the tremendous progress that we have made in correcting the distorting effects of the Earth’s atmosphere with high-angular resolution imaging. The most recent technology of adaptive optics is now opening up new horizons and allowing us to learn even more about this black hole at the center of our galaxy – how it was formed, how it grows and how to correctly describe the properties of space and time in the vicinity of such an exotic object.”

Another thing that helped the research was the competition between the two research teams, Ghez said. 

“There’s nothing like competition to spur you on,” Ghez said. “It’s been a very collegial, constructive competition.”

And all that competition spins back around to drive the technology.

“Andrea has been a passionate and tireless user of the Keck telescopes and our high-angular-resolution imaging capabilities to study the Galactic Center and its super-massive black hole,” said Keck Observatory director Taft Armandroff. “I have no doubt that our adaptive optics capabilities are stronger and more tailored to address astrophysical questions by virtue of Andrea’s involvement and that of her team.”

The Crafoord Prize is an annual award that rotates between the disciplines of astronomy, mathematics, geosciences, biosciences and arthritis research. This year’s honorees came from mathematics and astronomy, fields last recognized in 2008. The prize will be presented by the King of Sweden, at an award ceremony held on May 15, 2012. Andrea Ghez will be the first woman to be awarded this prize in any field in its 30-year history.

The W. M. Keck Observatory operates two 10-meter optical/infrared telescopes on the summit of Mauna Kea on the Big Island of Hawaii. The twin telescopes feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectroscopy and a world-leading laser guide star adaptive optics system which cancels out much of the interference caused by Earth’s turbulent atmosphere. The Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.

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