Why are telescopes like JWST orbiting Earth able to perform so much better than telescopes on Earth that aren’t restricted by their size?
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JWST is not orbiting Earth. It’s orbiting the Sun, 1.5 million kilometers (1 million miles) away from the Earth at what is called the second Lagrange point or L2. L2 is a point of equilibrium between the gravitational pull of the Sun and Earth. It lies on a line through the Sun and Earth, beyond Earth. This allows the satellite’s large sunshield to protect the telescope from the light and heat of the Sun and Earth (and Moon).
The sun shield also protects the sensitive mirrors and instruments from the spacecraft bus, which contains the computer, communications antenna, and steering mechanisms. There’s a huge temperature difference between the hot and cold sides of the shield. The cold is necessary because it’s an infrared telescope, and any nearby heat would hurt its ability to detect very faint infrared signals from incredibly distant objects.
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