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Why the Webb Telescope Lives at a Lagrange Point
韦布望远镜为何放在拉格朗日点
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The James Webb Space Telescope orbits not around Earth, but near the Sun-Earth L2 point — one of five stable gravitational zones.
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At L2, the telescope stays in constant alignment with Earth and the Sun, allowing its sunshield to block heat and light from both bodies.
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This position keeps its infrared sensors extremely cold, which is essential for detecting faint heat signals from distant galaxies.
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Unlike Hubble, which circles Earth every 95 minutes, Webb’s L2 orbit minimizes fuel use and avoids frequent eclipses.
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Gravitational forces at L2 balance perfectly, so only tiny thruster adjustments are needed to maintain position over years.
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Engineers chose L2 because it offers an unobstructed, thermally stable view of deep space — critical for observing cosmic origins.
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Although L2 is 1.5 million kilometers away, communication remains reliable via NASA’s Deep Space Network antennas.
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No human maintenance is possible there, so Webb was designed for full autonomy and redundancy before launch.