What is meant in astronomy by the phrase "adaptive optics?
a. The mirrors and eyepiece of a large telescope are spring-loaded to allow them to return quickly to a known position.
b. Slow modifications are made to the pointing controls of a telescope to keep it pointed toward the target object.
c. The optical elements of a telescope are placed on vibration-free mounts to compensate for ground motion.
d. A laser is used to point the telescope more accurately at the source.
e. Rapid modifications are made to the tilt and location of the elements of a telescope to correct for the effects of atmospheric and instrumental distortion.

Adaptive optics is a method used in several astronomical observatories to counteract in real time the effects of the Earth's atmosphere on the formation of astronomical images.

This is done through the insertion into the optical path of the telescope of sophisticated deformable mirrors supported by a set of computationally controlled actuators. Thus obtaining clear images despite the effects of atmospheric turbulence that cause the unwanted distortion.

It should be noted that with this technique it is also necessary to have a moderately bright reference star that is very close to the object to be observed and studied. However, it is not always possible to find such stars, so a powerful laser beam is used to point towards the Earth's upper atmosphere and create artificial stars.