{
  "abstract": "The compact red source “Capotauro”, discovered in deep JWST imaging in 2025, has been suggested as a possible galaxy candidate at redshift z ≃ 32 on account of its extreme NIRCam colours. However, given the lack of evidence that this source is spatially resolved, a very cool brown dwarf, at a distance consistent with the scale-height of the Milky Way stellar disc (≃ 500 pc), provides an alternative explanation of the observed photometry. Here we exploit new medium-band NIRCam imaging obtained ≃ 3.5 years after the discovery data to test this hypothesis. Using filter-dependent point-spread-function fitting, a robust local relative astrometric frame defined by 68 compact reference sources, and a joint four-image injection–recovery analysis, we show that Capotauro has moved by 132 ± 20 mas over the 3.5-yr interval span of the observations, ruling out the possibility that it is an extragalactic source (galaxy, AGN, or supernova) at >6σ. The observed apparent proper motion is $(\\mu _\\xi ,\\mu _\\eta )=(+9.4^{+6.4}_{-4.8},-35.6^{+5.1}_{-5.9})$ mas yr−1, or $37.6^{+5.5}_{-5.6}$ mas yr−1 in total. Through comparison of its photometric spectral energy distribution with empirical templates, we find that Capotauro is best described as a brown dwarf of spectral type Y1.0 ± 0.5 (${T_{\\rm eff}} \\approx 350$ K) at a distance of 730 ± 110 pc (although the existing data and spectral templates are insufficient to rule out an even colder, later-type brown dwarf). Capotauro is thus one of the most distant Y dwarfs found to date, as expected given its discovery in a deep JWST extragalactic survey field. This result demonstrates the value of multi-epoch imaging for identifying substellar contaminants among the most extreme photometric-redshift candidates.",
  "abstract_shown": true,
  "affiliations": [
    "Institute for Astronomy, University of Edinburgh , Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ ,",
    "Centre for Exoplanet Science, University of Edinburgh , Edinburgh, EH9 3HJ ,",
    "Institute of Astronomy , KU Leuven, Celestijnenlaan 200D, B-3001 Leuven ,",
    "Leuven Gravity Institute, KU Leuven , Celestijnenlaan 200D, box 2415, 3001 Leuven ,",
    "Armagh Observatory and Planetarium , College Hill, Armagh, BT61 9DG, N. Ireland ,",
    "NSF’s National Optical-Infrared Astronomy Research Laboratory , 950 N. Cherry Avenue, Tucson, AZ 85719 ,",
    "University College London Department of Physics and Astronomy, , Gower Street, London WC1E 6BT ,"
  ],
  "article_type": null,
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  "author_total": 16,
  "authors": [
    {
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        0
      ],
      "name": "F-Y F Liu",
      "orcid": "0000-0003-1386-3676"
    },
    {
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        0
      ],
      "name": "D J McLeod"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "B J Sutlieff"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "T J Dupuy"
    },
    {
      "affs": [
        0
      ],
      "name": "J S Dunlop"
    },
    {
      "affs": [
        0
      ],
      "name": "X Chen",
      "orcid": "0009-0005-9339-2369"
    },
    {
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        0
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      "name": "R J McLure"
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    {
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        0
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      "name": "H-H Leung",
      "orcid": "0000-0003-0486-5178"
    },
    {
      "affs": [
        0
      ],
      "name": "S Antonogiannaki"
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    {
      "affs": [
        0
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      "name": "C Bondestam"
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    {
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        2,
        3
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      "name": "E Laplace"
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    {
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        4
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      "name": "R Begley",
      "orcid": "0000-0003-0629-8074"
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    {
      "affs": [
        0
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      "name": "A C Carnall",
      "orcid": "0000-0002-1482-5818"
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    {
      "affs": [
        0
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      "name": "F Cullen"
    },
    {
      "affs": [
        5
      ],
      "name": "C T Donnan",
      "orcid": "0000-0002-7622-0208"
    },
    {
      "affs": [
        6
      ],
      "name": "R S Ellis"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/946mc6tft5khb.bib",
  "cited_by": 0,
  "doi": "10.1093/mnras/stag2055",
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  "id": "946mc6tft5khb",
  "issns": [
    "0035-8711",
    "1365-2966"
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  "landing_url": "https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stag2055/9003823",
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  "licence_label": "CC BY 4.0",
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      "3103|Stellar, planetary, and galactic studies"
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  "pdf_url": "https://academic.oup.com/mnras/advance-article-pdf/doi/10.1093/mnras/stag2055/72561131/stag2055.pdf",
  "pmcid": null,
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  "published": "2026-10-28",
  "publisher": "Oxford University Press (OUP)",
  "ris": "https://research.draconitic.com/paper/946mc6tft5khb.ris",
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      "origin": "openalex:3103|Stellar, planetary, and galactic studies",
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  "title": "A clear detection of proper motion confirms that the claimed z ≃ 32 galaxy candidate, “Capotauro”, is a Y-type brown dwarf",
  "title_text": "A clear detection of proper motion confirms that the claimed z ≃ 32 galaxy candidate, “Capotauro”, is a Y-type brown dwarf",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:18:17Z",
  "url": "https://research.draconitic.com/paper/946mc6tft5khb",
  "venue": "Monthly Notices of the Royal Astronomical Society",
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}