The task of detecting an Earth-like planet poses a significant challenge due to the fact that the planet is approximately 10 billion times fainter than its parent star. This makes it extremely difficult to capture the faint light reflected from the planet using conventional telescopes. To overcome this obstacle, scientists use a coronagraph to block most of the starlight and focus on the faint light reflected from the planet.
However, even with a coronagraph, detecting an Earth-like planet requires an exceptional level of precision in both the telescope and its optical quality or wavefront. This is because any instability in the telescope’s optics, such as misalignment between mirrors or changes in mirror shape, can cause glare that masks the planet. As a result, scientists must control these factors with utmost accuracy, down to 10s of picometers (pm), which is roughly equivalent to the size of a hydrogen atom.
This high level of precision required for detecting an Earth-like planet highlights the extraordinary challenges faced by astronomers in this field. Despite these challenges, advances in technology and techniques continue to make it possible for scientists to push back the boundaries of what we know about our universe and search for potential planets beyond our own solar system.