An optical system that enables rapid fluctuations in a telescope's image
quality, caused by atmospheric turbulence, to be corrected in fractions
of a second. These fluctuations are measured by a wavefront sensor
that uses a reference star to measure the distortions that are taking place.
The reference star is typically a reasonably bright star close in the sky
to the object under study but may also be the object itself or a reflected
laser beam that serves as an artificial reference star. The measured distortions
are then removed with a phase corrector – typically
a very thin mirror in the light path of the telescope that can be rapidly
deformed by actuators to the equivalent shape of the wavefront, which must
be subtracted to produce a sharp image.
Unlike active optics, adaptive optics provides
real-time response and allows the image quality of ground-based instruments
to rival that of telescopes operating in space. It is used in conjunction
with many new telescopes including the Very Large
Telescope, the Large Binocular Telescope,
and the Keck Telescopes. Adaptive optics was
pioneered at the Center for Astronomical Adaptive
Optics and will be used extensively, in conjunction with another new
technique known as nulling interferometry,
in the search for extrasolar planets
and circumstellar dust disks.
- Angel, J. R. P. "Ground-based Imaging of Extrasolar Planets Using
Adaptive Optics," Nature, 368, 203 (1994).
- Angel, J. R. P. "Taking Adaptive Optics to the Limit to Image Extrasolar
Planets," Astrophysics & Space Science, 223, 136 (1995).
to adaptive optics (ESO)
AND OPTICAL PHENOMENA
PLANETS AND SUBSTELLAR OBJECTS