The James Webb Space Telescope is making groundbreaking discoveries about the universe by observing distant galaxies, stars, and exoplanets. However, its unique orbit around the Sun’s second Lagrange point makes it impossible for it to look at three of our own planets: Mercury, Venus, and Earth.
Located about 1.5 million kilometers from Earth on the opposite side of the Sun, the telescope’s stable position minimizes fuel use but also prevents it from observing nearby celestial bodies. The reason lies in the extreme sensitivity of its instruments, which require precise temperature control to function.
The James Webb Space Telescope orbits at a point where it faces away from the Sun and towards the deep cosmos. This design allows it to shield its mirrors and instruments from bright hot sources like the Earth, Sun, and Moon, keeping them cool to operate effectively. However, if it attempted to look at our inner planets, it would be exposed to intense heat and sunlight, potentially damaging its delicate instruments.
Despite this limitation, the James Webb Space Telescope can still observe other planets in our Solar System, including Mars, Jupiter, Saturn, Uranus, Neptune, and several of their moons. It has also studied asteroids and Kuiper Belt objects like Pluto, all located far enough from the Sun’s glare to be safely observed. The telescope’s design is a careful balance of engineering and science, ensuring it unlocks the secrets of the distant Universe without compromising its instruments’ functionality.
Source: https://www.skyatnightmagazine.com/space-science/webb-earth-venus-mercury