 |
||||||||
 |
||||||||
 |
 |
 |
 |
 |
 |
 |
 |
 |
Cultural Resources > ObservatoriesAdaptive Optics: UC Sees More Clearly Adaptive optics refers to optical systems which adapt to compensate for optical effects introduced by the medium between the object and its image leading to appreciably sharper images. Learn more about this field at UC adaptive optics
centers: Adaptive optics technology can remove the blurring
effect of the Earth's atmosphere that has long plagued astronomers,
allowing ground-based telescopes to achieve a clarity of vision
previously attainable only by space-based instruments. Current adaptive
optics (AO) systems are able to make images that are superior to
those of the Hubble Space Telescope in infrared light. "Adaptive optics is working well today on several large telescopes, but for the giant telescopes of the future, the adaptive optics systems will have to be significantly more sophisticated than they are now," said Jerry Nelson, director of the Center for Adaptive Optics (CfAO), a National Science Foundation (NSF) Science and Technology Center based at UCSC. Established in 1999, the CfAO plays a key role in the advancement of adaptive optics technology through a network of partners that includes academic institutions, national laboratories, and companies in related industries. Already, astronomers have been thrilled by the results achieved with adaptive optics systems operating at some of the world's major observatories. At the W. M. Keck Observatory in Hawaii, for example, adaptive optics technology has produced eightfold improvements in image quality, said the obervatory's director, Frederic H. Chaffee. "When the Keck II Telescope was first 'fitted' with adaptive optics in 1999, the effect was as dramatic as someone who has had 20/150 vision all his life getting fitted with glasses and seeing the world with 20/20 eyes for the first time," Chaffee said. "With adaptive optics, the Keck Telescopes are giving astronomers unprecedented views of the planets and their moons, nearby stars, and distant galaxies. It's a whole new universe out there." Andrea Ghez, an associate director of the CfAO and professor of astronomy and physics at UCLA, is using the AO system on the Keck Telescopes to study the black hole at the center of our home galaxy, the Milky Way. Ghez first demonstrated the existence of a supermassive black hole at the galactic center using a technique called speckle interferometry, a precursor to adaptive optics. "It was sort of poor-man's adaptive optics, and it provided very limited information compared to what we are now able to gather using adaptive optics," she said. "For example, we can now start to use spectroscopy to understand the types of stars that are located in the vicinity of the black hole, and we are getting some very surprising results." An adaptive optics system uses a point source of light as a reference beacon to measure the effects of the atmosphere. The light is analyzed by a detector, called a wavefront sensor, that measures how the light waves were distorted as they passed through the atmosphere. The light collected by the telescope is then bounced off a deformable mirror that changes shape to counteract the distortions measured by the wavefront sensor. A high-speed computer calculates the necessary corrections several hundred times per second, enabling the system to respond to the constantly changing turbulence of the atmosphere. The light source for the reference beacon can be
a bright star in the sky—either the same star being studied
or a star adjacent to the object of interest, which might be a faint,
distant galaxy. Relying on these "natural" guide stars,
however, limits AO observations to the small fraction of the sky
that is close to relatively bright stars—only about 1 percent
of the sky. So researchers have devised ways of creating artificial
guide stars using powerful lasers. |
|