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Why were Kuiper belt objects difficult to detect before the 1990s?

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Kuiper belt binary object — Kuiper belt An artist's rendition of a binary object in the Kuiper belt. The two objects depicted orbit each other at the edge of the solar system.

Before the 1990s, objects in the Kuiper belt were difficult to detect primarily because the necessary technological infrastructure had not yet been developed. Specifically, astronomers lacked the required large telescopes and sufficiently sensitive light detectors to identify these distant, faint bodies.1

Although the existence of the Kuiper belt had been theorized for decades—with astronomers like Kenneth E. Edgeworth and Gerard P. Kuiper proposing that a reservoir of icy bodies existed beyond Neptune—direct observation remained elusive until 1992. In that year, astronomers David Jewitt and Jane Luu successfully discovered (15760) 1992 QB1, which served as the first confirmed Kuiper belt object (KBO). This breakthrough demonstrated the feasibility of detecting these objects, leading to the discovery of approximately 1,500 additional KBOs within the following two decades.21