Detecting an Earth-like planet presents a significant challenge due to the fact that the planet is approximately 10 billion times fainter than its parent star. The key obstacle lies in the need to block almost all of the star’s light in order to capture the faint light reflected from the planet. This requires the use of a coronagraph to block the starlight. However, any instability in the telescope’s optics, such as misalignment between mirrors or a change in the mirror’s shape, can lead to leakage of starlight and cause glare that masks the planet.
As a result, detecting an Earth-like planet using a coronagraph necessitates precise control of both the telescope and the instrument’s optical quality, or wavefront, to an exceptional level of 10s of picometers (pm). This is roughly on the order of the size of a hydrogen atom, emphasizing the extraordinary precision needed for this endeavor. To achieve this level of precision, scientists must use advanced techniques such as adaptive optics and active optics to correct for any distortions in the telescope’s optical path. Additionally, they must carefully calibrate and align all components of the instrument to ensure that they are working together seamlessly. Despite these challenges, recent advancements in technology have made it possible for scientists to detect Earth-like planets around other stars with unprecedented accuracy and sensitivity.