Question

multiple - choice question
why does the jwst have to be really cold?
so that its superconducting magnets can transmit electricity efficiently.
so the mirrors dont expand and break.
so it doesnt give off any infrared radiation of its own which would interfere with its ability to detect infrared from far away.

Explanation:

The James - Webb Space Telescope (JWST) is an infrared observatory. Heat causes objects to emit infrared radiation. If the JWST were warm, its own infrared emissions would interfere with its ability to detect faint infrared signals from distant celestial objects. It does not rely on superconducting magnets for its main function, and thermal expansion of mirrors is not the main reason for keeping it cold.

Answer:

So it doesn't give off any infrared radiation of its own which would interfere with its ability to detect infrared from far away.