U.S. and Swiss scientists discover how to used light refraction to gather needed data
POSTED: 1:30 a.m. HST, Jul 17, 2010
Astronomers at Mauna Kea's Keck Observatory have unlocked a powerful new tool to study the brightest and most mysterious bodies in the night sky.
Scientists from the California Institute of Technology and Switzerland's Ecole Polytechnique Federale de Lausanne announced Thursday they have found a way to use bent light from distant celestial bodies to determine the size of galaxies that house quasars, large bodies likely created by light escaping from high-energy black holes at the galaxies' center.
Astronomers have tried for decades to gather data on the host galaxies because light from the quasars is thousands of times greater than the galaxies surrounding them.
"It is a bit like staring into bright car headlights and trying to discern the color of their rims," Ecole Polytechnique astronomer Frederic Courbin said in a news release.
The discovery builds on the celestial phenomenon of gravitational lensing, predicted by Albert Einstein's theory of relativity. When light from a distant galaxy encounters a large mass -- a quasar or another large galaxy, for instance -- the gravitational pull of the interfering body is enough to bend the light, warping images of the body received by telescopes on the other side of the large mass. Instead of seeing a single image of the distant galaxy, telescopes on Earth see the refracted light as two or more magnified images of the background galaxy.
"If you place a big mass smack in the line of sight, then it will bend the light rays," Caltech professor George Djorgovski said in an interview. "It can split the image of the background source."
Exploiting this phenomenon, astronomers can now calculate the mass of a foreground galaxy containing a quasar -- the interfering body -- by measuring the refraction of light from background sources.
"This project will offer a new way to weight this lensing quasar and its host galaxy ... in a completely different way with respect to what has been used so far," Ecole Polytechnique astrophysics professor Georges Meylan said. "This confirmation of what we suspected to be an interesting object was more than welcome."
According to Meylan, the team was searching for candidate quasars on which to run the experiment for more than a year before they found success atop Mauna Kea. The Keck Observatory, he said, was pivotal to the experiment's success.
"Keck telescope was essential because of its collecting power -- it is one of the largest telescopes in the world, a high-technology facility providing us with the sharpest possible images," Meylan said in an e-mail.
The project was wrapped up early this year, and the team will publish its findings in the journal Astronomy & Astrophysics. The scientists also hope to replicate the technique on other quasars, and have begun researching other candidates.
"Quasars are the most fascinating objects in the universe," Djorgovski said. "This provides us with a new way to study these strange objects."