Final answer:
The essential component of a coronagraph for directly imaging an exoplanet is adaptive optics, which compensates for the blurring effect of Earth's atmosphere.
Step-by-step explanation:
The essential component of a coronagraph that is used to remove or reduce diffracted light and enable direct imaging of an exoplanet is adaptive optics.
Adaptive optics is a technique that compensates for the blurring effect of Earth's atmosphere using a small flexible mirror placed in the beam of a telescope. A sensor measures atmospheric distortions and sends instructions to the mirror to adjust its shape, bringing the light to a sharper focus. With adaptive optics, ground-based telescopes can achieve high resolutions in the infrared region of the spectrum.