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Monthly Notices of the Royal Astronomical Society  ·  29 August 2026  ·  From issue 29

H I Absorbers as Beacons of Hidden Structure at z ~ 3: Multi-Component, Metal-Rich Absorption System near a Protocluster

A giant hydrogen gas cloud sits far from a known galaxy cluster, not inside it.

Kentaro Koretomo, Nobunari Kashikawa et al.

A huge, unexpected cloud of hydrogen gas was found far from a distant galaxy cluster, not inside it. The cloud stretched across a distance equal to about 40 million light years and was made of five separate pieces. One piece had unusually high levels of heavy elements. This may point to a hidden second cluster or to gas flowing in and out of a massive galaxy.

The number about 40 million light years across, five pieces

The size and structure of the unexpected hydrogen gas cloud found near a distant galaxy cluster.

One quasar sightline in the early universe, not a full 3D map.

Integrity screen: passed (3 checks) Checked 31 August 2026. Retraction record: none. DOI resolves at doi.org. Metadata record found (Monthly Notices of the Royal Astronomical Society). Read the source

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