image: Model image of the massive and fast-spinning star Regulus compared to the Sun.
Credit: Courtest: CHARA Array
ATLANTA — Georgia State University’s Center for High Angular Resolution Astronomy (CHARA) Array is marking the 20th anniversary of its first scientific results, published in the July 20, 2005, issue of the Astrophysical Journal. These two papers — one revealing new astronomical insights about the massive star Regulus, and the other detailing how the CHARA Array enabled the discoveries — were led by GSU scientists Hal McAlister and Theo ten Brummelaar.
The CHARA Array uses six telescopes spread across Mount Wilson, Calif., that act together as one enormous telescope. The array is able to see stars in detail, which helps scientists study their properties better than any other instrument in the world.
“The CHARA Array stands as a powerful testament to Georgia State’s commitment to pioneering research and international scientific collaboration,” said Georgia State Provost and Executive Vice President for Academic Affairs Nicolle Parsons-Pollard. “Over the past two decades, it has enabled groundbreaking discoveries that have deepened our understanding of the universe. With its expanding capabilities and worldwide reach, we are proud to support CHARA as it continues to drive innovation and advance science on a global scale.”
The study by McAlister focused on the hot star Regulus (or alpha Leo). Regulus has a mass four times greater than the Sun’s mass, and it rotates very quickly, spinning once every 0.7 days compared to the 25 days of the Sun’s equatorial spin. The CHARA observations showed that this rapid spin causes the star to bulge out toward its equator, so it presents an oblong shape in the sky.
Now a Regents' Professor Emeritus of Astronomy, McAlister first proposed the ambitious CHARA project to the Arts & Sciences dean in 1983. Since retiring in 2015, he has watched with pride as CHARA has continued to flourish.
“It’s been a joy to witness CHARA grow to even greater heights thanks to the dedication of so many over the years,” he said.
The other paper, by ten Brummelaar, described how the many components of the CHARA Array work together to give it its exquisite, close-up views. These two papers have been cited some 600 times by other scientists.
Ten Brummelaar, who served as director of the CHARA Array until his retirement in 2022, was honored with the Fizeau Lifetime Achievement Award for his leadership and enduring contributions to astronomical optical interferometry.
“At the time, Georgia State University wasn’t the large research university it is now, and very few people thought we’d get the funding, let alone be successful at building the CHARA Array,” ten Brummelaar said of the early days of the project. “We were a very small team of people with little history of designing and building large instruments like this. Nevertheless, we had a great deal of support, both financial and moral, from the university, and now CHARA and GSU are leaders in the field of ground-based optical interferometry and the astrophysics it enables."
Since these works were published two decades ago, there have been 276 research papers published by over 500 scientists from around the globe based on studies with the CHARA Array. These studies examine all kinds of stars: young stars with disks, stars with magnetic storms, older stars ejecting their gas into space and orbiting pairs of binary stars.
“We knew in 2005 that the array would open a new window on the universe,” said CHARA Director Douglas Gies. “But it is astonishing how much the array has revealed to us about the stars and their lives.”
Today, thanks to new research and technology, the array records light from across the spectrum with an efficiency unimagined in the early days of 2005. These new capabilities will enable more discoveries in the years ahead. Work is already underway on stars hosting planetary systems and distant supermassive black holes.
“The new cameras at the array can now determine how stars appear in the colors our eyes see as well those long wavelength, near-infrared colors,” said Array Director Gail Schaefer. “Thanks to contributions from astronomers from France, the United Kingdom, Australia and the U.S., we now have the best equipment to see the stars close up in great detail.”
The CHARA Array is funded by the National Science Foundation (grant AST-2407956). Institutional support for the CHARA Array is provided from Georgia State’s College of Arts & Sciences and the Office of the Provost.
For more information about Georgia State University research and its impact, visit research.gsu.edu. For more information about the CHARA Array visit the CHARA Array website.