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    "story_id": "mp-2026-09-25-006",
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    "headline": "A Dark-Galaxy Candidate Appeared Without Starlight",
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    "dek": "FAST found compact hydrogen, but deep optical imaging found no counterpart down to a faint surface-brightness limit.",
    "summary": "FAST found compact hydrogen, but deep optical imaging found no counterpart down to a faint surface-brightness limit.",
    "body_text": "A blind FAST hydrogen survey and DESI Legacy Survey imaging identified J1351+0039 as an isolated Reionization-Limited H I Cloud candidate. The object has an inferred neutral-hydrogen mass of 480,000 solar masses, no detected optical counterpart to a g-band surface-brightness limit of 28.1 magnitudes per square arcsecond, and an estimated dynamical mass of 130 million solar masses. The authors derive a dark-to-baryonic mass ratio near 200, while describing the classification as a promising candidate rather than a settled dark-galaxy discovery.",
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    "tags": [
      "FAST",
      "dark galaxy",
      "neutral hydrogen"
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    {
      "source_id": "source-2026-09-25-006",
      "title": "arXiv preprint 2609.29852",
      "publisher": "arXiv",
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      "published_at": "2026-09-24T10:17:31.000-04:00",
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    "title": "A Dark-Galaxy Candidate Appeared Without Starlight",
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