Detecting an Earth-like planet is a significant challenge due to the fact that it 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, which blocks starlight by using an occulting disk or mask placed between the telescope and the star. However, any instability in the telescope’s optics can lead to leakage of starlight and cause glare that masks the planet.
To detect an Earth-like planet using a coronagraph, precise control of both the telescope and the instrument’s optical quality, or wavefront, is necessary. This requires exceptional levels of control to be achieved with high levels of accuracy, typically on the order of 10s of picometers (pm). This level of precision is roughly equivalent to the size of a hydrogen atom, emphasizing just how challenging this endeavor truly is.
In summary, detecting an Earth-like planet presents significant challenges due to its faintness compared to its parent star. These challenges can be overcome through careful calibration and precise control over both the telescope and instrumentation used for detection. However, achieving these levels of precision requires extraordinary efforts and attention to detail.