TOI-7169 b: A Hot Jupiter Transiting a Metal-poor Star

Joshua D. Simon; Joseph E. Rodriguez; Jhon Yana Galarza; David W. Latham; Victoria DiTomasso; Karen A. Collins; Jack Schulte; Anirudh Chiti; Samuel N. Quinn; Mohammad K. Mardini; Shubham Kanodia; Johanna K. Teske; Peter S. Ferguson; Samuel W. Yee; T. G. Tan; Khalid Alsubai; Khalid Barkaoui; Zouhair Benkhaldoun; Krzysztof Bernacki; Jaikrit Bhattacharya; Jerome P. de Leon; Sarah J. Deveny; Mark E. Everett; Izuru Fukuda; Akihiko Fukui; Michaël Gillon; Arvind F. Gupta; Steve B. Howell; Emmanuel Jehin; Gaia Lacedelli; Adam Lark; Colin Littlefield; Felipe Murgas; Norio Narita; Enric Palle; Hannu Parviainen; Adam Popowicz; Richard P. Schwarz; Avi Shporer; Abderahmane Soubkiou; Francis P. Wilkin

doi:10.3847/1538-3881/ae7f02

Jerome P. de Leon, Sarah J. Deveny, Mark E. Everett, Izuru Fukuda, Akihiko Fukui, Michaël Gillon, Arvind F. Gupta, Steve B. Howell, Emmanuel Jehin, Gaia Lacedelli, Adam Lark, Colin Littlefield, Felipe Murgas, Norio Narita, Enric Palle, Hannu Parviainen, Adam Popowicz, Richard P. Schwarz, Avi Shporer, Abderahmane Soubkiou, Francis P. Wilkin

^*Corresponding author for this work

Qatar Environment & Energy Research Institute

Carnegie Institution of Washington
Michigan State University
Universidad de Concepción
Harvard-Smithsonian Center for Astrophysics
Stanford University
Massachusetts Institute of Technology
University of Washington
University of California at Los Angeles
Perth Exoplanet Survey Telescope
Qatar Environment and Energy Research Institute
Instituto de Astrofísica de Canarias
University of Liege
University of Sharjah
Cadi Ayyad University
Silesian University of Technology
Hamilton College
The University of Tokyo
Bay Area Environmental Research Institute
NASA Ames Research Center
NSF NOIRLab
University of La Laguna
National Institutes of Natural Sciences - AstroBiology Center
Union College

Research output: Contribution to journal › Article › peer-review

Abstract

Most known planets are found around metal-rich host stars, which has made it difficult to determine whether a lower metallicity limit for planet formation exists and how the properties of planets born in low-metallicity environments may differ from those with metal-rich origins. We present the discovery and characterization of TOI-7169 b (TIC 372048733 b), a hot Jupiter that is orbiting a spectroscopically confirmed metal-poor ([Fe/H] = −0.72 ± 0.05) host star. Based on photometry from TESS and follow-up ground-based imaging, we measure an orbital period of (Formula presented) 3.4373125−0.0000019+0.0000020 days and a planetary radius of 1.475 ± 0.029 R_Jup. We use TRES spectroscopy to determine a mass for TOI-7169 b of 0.41 ± 0.14 M_Jup. The planet is therefore inflated, with a low density of (Formula presented) 0.159−0.054+0.055 g cm⁻³. We also characterize the host star, showing that TOI-7169 is ancient (12.3 ± 0.6 Gyr) and α enhanced ([α/Fe] ≈ 0.3), but with a Galactocentric orbit that is confined to the thin disk. TOI-7169 is perhaps the oldest and most metal-poor star currently known to host a transiting giant planet. Future transmission spectroscopy probing the atmosphere of TOI-7169 b may provide insight into the effect of metallicity on the physical properties of giant planets.

Original language	English
Article number	118
Journal	Astronomical Journal
Volume	172
Issue number	2
DOIs	https://doi.org/10.3847/1538-3881/ae7f02
Publication status	Published - 1 Aug 2026

Keywords

Exoplanet astronomy (486)
Exoplanets (498)
Hot Jupiters (753)
Milky Way disk (1050)
Population II stars (1284)
Transit photometry (1709)

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Simon, J. D., Rodriguez, J. E., Yana Galarza, J., Latham, D. W., DiTomasso, V., Collins, K. A., Schulte, J., Chiti, A., Quinn, S. N., Mardini, M. K., Kanodia, S., Teske, J. K., Ferguson, P. S., Yee, S. W., Tan, T. G., Alsubai, K., Barkaoui, K., Benkhaldoun, Z., Bernacki, K., ... Wilkin, F. P. (2026). TOI-7169 b: A Hot Jupiter Transiting a Metal-poor Star. Astronomical Journal, 172(2), Article 118. https://doi.org/10.3847/1538-3881/ae7f02

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title = "TOI-7169 b: A Hot Jupiter Transiting a Metal-poor Star",

abstract = "Most known planets are found around metal-rich host stars, which has made it difficult to determine whether a lower metallicity limit for planet formation exists and how the properties of planets born in low-metallicity environments may differ from those with metal-rich origins. We present the discovery and characterization of TOI-7169 b (TIC 372048733 b), a hot Jupiter that is orbiting a spectroscopically confirmed metal-poor ([Fe/H] = −0.72 ± 0.05) host star. Based on photometry from TESS and follow-up ground-based imaging, we measure an orbital period of (Formula presented) 3.4373125−0.0000019+0.0000020 days and a planetary radius of 1.475 ± 0.029 RJup. We use TRES spectroscopy to determine a mass for TOI-7169 b of 0.41 ± 0.14 MJup. The planet is therefore inflated, with a low density of (Formula presented) 0.159−0.054+0.055 g cm−3. We also characterize the host star, showing that TOI-7169 is ancient (12.3 ± 0.6 Gyr) and α enhanced ([α/Fe] ≈ 0.3), but with a Galactocentric orbit that is confined to the thin disk. TOI-7169 is perhaps the oldest and most metal-poor star currently known to host a transiting giant planet. Future transmission spectroscopy probing the atmosphere of TOI-7169 b may provide insight into the effect of metallicity on the physical properties of giant planets.",

keywords = "Exoplanet astronomy (486), Exoplanets (498), Hot Jupiters (753), Milky Way disk (1050), Population II stars (1284), Transit photometry (1709)",

author = "Simon, \{Joshua D.\} and Rodriguez, \{Joseph E.\} and \{Yana Galarza\}, Jhon and Latham, \{David W.\} and Victoria DiTomasso and Collins, \{Karen A.\} and Jack Schulte and Anirudh Chiti and Quinn, \{Samuel N.\} and Mardini, \{Mohammad K.\} and Shubham Kanodia and Teske, \{Johanna K.\} and Ferguson, \{Peter S.\} and Yee, \{Samuel W.\} and Tan, \{T. G.\} and Khalid Alsubai and Khalid Barkaoui and Zouhair Benkhaldoun and Krzysztof Bernacki and Jaikrit Bhattacharya and \{de Leon\}, \{Jerome P.\} and Deveny, \{Sarah J.\} and Everett, \{Mark E.\} and Izuru Fukuda and Akihiko Fukui and Micha{\"e}l Gillon and Gupta, \{Arvind F.\} and Howell, \{Steve B.\} and Emmanuel Jehin and Gaia Lacedelli and Adam Lark and Colin Littlefield and Felipe Murgas and Norio Narita and Enric Palle and Hannu Parviainen and Adam Popowicz and Schwarz, \{Richard P.\} and Avi Shporer and Abderahmane Soubkiou and Wilkin, \{Francis P.\}",

note = "Publisher Copyright: {\textcopyright} 2026. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.",

year = "2026",

month = aug,

day = "1",

doi = "10.3847/1538-3881/ae7f02",

language = "English",

volume = "172",

journal = "Astronomical Journal",

issn = "0004-6256",

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Simon, JD, Rodriguez, JE, Yana Galarza, J, Latham, DW, DiTomasso, V, Collins, KA, Schulte, J, Chiti, A, Quinn, SN, Mardini, MK, Kanodia, S, Teske, JK, Ferguson, PS, Yee, SW, Tan, TG, Alsubai, K, Barkaoui, K, Benkhaldoun, Z, Bernacki, K, Bhattacharya, J, de Leon, JP, Deveny, SJ, Everett, ME, Fukuda, I, Fukui, A, Gillon, M, Gupta, AF, Howell, SB, Jehin, E, Lacedelli, G, Lark, A, Littlefield, C, Murgas, F, Narita, N, Palle, E, Parviainen, H, Popowicz, A, Schwarz, RP, Shporer, A, Soubkiou, A & Wilkin, FP 2026, 'TOI-7169 b: A Hot Jupiter Transiting a Metal-poor Star', Astronomical Journal, vol. 172, no. 2, 118. https://doi.org/10.3847/1538-3881/ae7f02

TY - JOUR

T1 - TOI-7169 b

T2 - A Hot Jupiter Transiting a Metal-poor Star

AU - Simon, Joshua D.

AU - Rodriguez, Joseph E.

AU - Yana Galarza, Jhon

AU - Latham, David W.

AU - DiTomasso, Victoria

AU - Collins, Karen A.

AU - Schulte, Jack

AU - Chiti, Anirudh

AU - Quinn, Samuel N.

AU - Mardini, Mohammad K.

AU - Kanodia, Shubham

AU - Teske, Johanna K.

AU - Ferguson, Peter S.

AU - Yee, Samuel W.

AU - Tan, T. G.

AU - Alsubai, Khalid

AU - Barkaoui, Khalid

AU - Benkhaldoun, Zouhair

AU - Bernacki, Krzysztof

AU - Bhattacharya, Jaikrit

AU - de Leon, Jerome P.

AU - Deveny, Sarah J.

AU - Everett, Mark E.

AU - Fukuda, Izuru

AU - Fukui, Akihiko

AU - Gillon, Michaël

AU - Gupta, Arvind F.

AU - Howell, Steve B.

AU - Jehin, Emmanuel

AU - Lacedelli, Gaia

AU - Lark, Adam

AU - Littlefield, Colin

AU - Murgas, Felipe

AU - Narita, Norio

AU - Palle, Enric

AU - Parviainen, Hannu

AU - Popowicz, Adam

AU - Schwarz, Richard P.

AU - Shporer, Avi

AU - Soubkiou, Abderahmane

AU - Wilkin, Francis P.

N1 - Publisher Copyright: © 2026. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

PY - 2026/8/1

Y1 - 2026/8/1

N2 - Most known planets are found around metal-rich host stars, which has made it difficult to determine whether a lower metallicity limit for planet formation exists and how the properties of planets born in low-metallicity environments may differ from those with metal-rich origins. We present the discovery and characterization of TOI-7169 b (TIC 372048733 b), a hot Jupiter that is orbiting a spectroscopically confirmed metal-poor ([Fe/H] = −0.72 ± 0.05) host star. Based on photometry from TESS and follow-up ground-based imaging, we measure an orbital period of (Formula presented) 3.4373125−0.0000019+0.0000020 days and a planetary radius of 1.475 ± 0.029 RJup. We use TRES spectroscopy to determine a mass for TOI-7169 b of 0.41 ± 0.14 MJup. The planet is therefore inflated, with a low density of (Formula presented) 0.159−0.054+0.055 g cm−3. We also characterize the host star, showing that TOI-7169 is ancient (12.3 ± 0.6 Gyr) and α enhanced ([α/Fe] ≈ 0.3), but with a Galactocentric orbit that is confined to the thin disk. TOI-7169 is perhaps the oldest and most metal-poor star currently known to host a transiting giant planet. Future transmission spectroscopy probing the atmosphere of TOI-7169 b may provide insight into the effect of metallicity on the physical properties of giant planets.

AB - Most known planets are found around metal-rich host stars, which has made it difficult to determine whether a lower metallicity limit for planet formation exists and how the properties of planets born in low-metallicity environments may differ from those with metal-rich origins. We present the discovery and characterization of TOI-7169 b (TIC 372048733 b), a hot Jupiter that is orbiting a spectroscopically confirmed metal-poor ([Fe/H] = −0.72 ± 0.05) host star. Based on photometry from TESS and follow-up ground-based imaging, we measure an orbital period of (Formula presented) 3.4373125−0.0000019+0.0000020 days and a planetary radius of 1.475 ± 0.029 RJup. We use TRES spectroscopy to determine a mass for TOI-7169 b of 0.41 ± 0.14 MJup. The planet is therefore inflated, with a low density of (Formula presented) 0.159−0.054+0.055 g cm−3. We also characterize the host star, showing that TOI-7169 is ancient (12.3 ± 0.6 Gyr) and α enhanced ([α/Fe] ≈ 0.3), but with a Galactocentric orbit that is confined to the thin disk. TOI-7169 is perhaps the oldest and most metal-poor star currently known to host a transiting giant planet. Future transmission spectroscopy probing the atmosphere of TOI-7169 b may provide insight into the effect of metallicity on the physical properties of giant planets.

KW - Exoplanet astronomy (486)

KW - Exoplanets (498)

KW - Hot Jupiters (753)

KW - Milky Way disk (1050)

KW - Population II stars (1284)

KW - Transit photometry (1709)

UR - https://www.scopus.com/pages/publications/105046015937

U2 - 10.3847/1538-3881/ae7f02

DO - 10.3847/1538-3881/ae7f02

M3 - Article

AN - SCOPUS:105046015937

SN - 0004-6256

VL - 172

JO - Astronomical Journal

JF - Astronomical Journal

IS - 2

M1 - 118

ER -

TOI-7169 b: A Hot Jupiter Transiting a Metal-poor Star

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