A Cold and Superpuffy Planet on a Prograde Orbit

Juan I. Espinoza-Retamal; Rafael Brahm; Cristobal Petrovich; Andrés Jordán; Thomas Henning; Trifon Trifonov; Joshua N. Winn; Erika Rea; Maximilian N. Günther; Abdelkrim Agabi; Philippe Bendjoya; Hareesh Bhaskar; François Bouchy; Márcio Catelan; Carolina Charalambous; Vincent Deloupy; George Dransfield; Jan Eberhardt; Néstor Espinoza; Alix V. Freckelton; Tristan Guillot; Melissa J. Hobson; Matías I. Jones; Monika Lendl; Djamel Mekarnia; Diego J. Muñoz; Louise D. Nielsen; Felipe I. Rojas; François-Xavier Schmider; Elyar Sedaghati; Guđmundur Stefánsson; Stephanie Striegel; Olga Suarez; Marcelo Tala Pinto; Mathilde Timmermans; Amaury H. M. J. Triaud; Stéphane Udry; Solène Ulmer-Moll; Carl Ziegler

doi:10.3847/2041-8213/ae2bfa

A Cold and Superpuffy Planet on a Prograde Orbit

Juan I. Espinoza-Retamal^*
, Rafael Brahm
, Cristobal Petrovich
, Andrés Jordán
, Thomas Henning
, Trifon Trifonov
, Joshua N. Winn
, Erika Rea
, Maximilian N. Günther
, Abdelkrim Agabi
, Philippe Bendjoya
, Hareesh Bhaskar
, François Bouchy
, Márcio Catelan
, Carolina Charalambous
, Vincent Deloupy
, George Dransfield
, Jan Eberhardt
, Néstor Espinoza
, Alix V. Freckelton

Tristan Guillot, Melissa J. Hobson, Matías I. Jones, Monika Lendl, Djamel Mekarnia, Diego J. Muñoz, Louise D. Nielsen, Felipe I. Rojas, François-Xavier Schmider, Elyar Sedaghati, Guđmundur Stefánsson, Stephanie Striegel, Olga Suarez, Marcelo Tala Pinto, Mathilde Timmermans, Amaury H. M. J. Triaud, Stéphane Udry, Solène Ulmer-Moll, Carl Ziegler

^*Corresponding author for this work

Physics and Astronomy

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

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Abstract

We report the discovery of TOI-4507 b, a transiting sub-Saturn with a density <0.2 g cm⁻³ on a 105 days prograde orbit around a 700 Myr old F star. The transits were detected using data from TESS as well as the Antarctic telescope ASTEP. A joint analysis of the light curves and radial velocities from HARPS, FEROS, and CORALIE confirmed the planetary nature of the signal, by limiting the mass to be below 20 M_⊕ at 95% confidence. The radial velocities also exhibit the Rossiter–McLaughlin effect and imply that the planet orbits the star in a prograde orbit with a sky-projected obliquity λ = −15⁺⁵⁰₋₄₄° (∣λ∣ < 80° at 3σ). With these characteristics, TOI-4507 is one of the longest-period systems for which the stellar obliquity has been measured, and the planet is among the longest-period and youngest “superpuff” planets yet discovered.

Original language	English
Article number	L13
Number of pages	14
Journal	Astrophysical Journal Letters
Volume	996
Issue number	1
Early online date	30 Dec 2025
DOIs	https://doi.org/10.3847/2041-8213/ae2bfa
Publication status	Published - 1 Jan 2026

Keywords

Transit photometry
Exoplanets
Cold Neptunes
Radial velocity

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10.3847/2041-8213/ae2bfaLicence: Creative Commons: Attribution (CC BY)

EspinozaRetamalJI2026ColdFinal published version, 8.2 MBLicence: Creative Commons: Attribution (CC BY)

1 Active
3 Finished

Temperate planets from Chile & Antarctica
Triaud, A. (Principal Investigator)
SCIENCE & TECHNOLOGY FACILITIES COUNCIL
1/04/24 → 31/03/27
Project: Research
An upgrade to the mount of the ASTEP telescope
Vecchio, A. (Co-Investigator), Triaud, A. (Principal Investigator), Nicholl, M. (Co-Investigator) & Schmidt, P. (Co-Investigator)
SCIENCE & TECHNOLOGY FACILITIES COUNCIL
1/07/21 → 31/12/21
Project: Research Councils
H2020_ERC_BEBOP
Triaud, A. (Principal Investigator)
European Commission
1/11/18 → 31/10/24
Project: EU
Red-Enhanced Cameras to Seek Rocky Planets Transiting Ultra-Cool Dwarfs
Chaplin, B. (Co-Investigator) & Triaud, A. (Principal Investigator)
SCIENCE & TECHNOLOGY FACILITIES COUNCIL
1/10/18 → 20/09/19
Project: Research Councils

Cite this

Espinoza-Retamal, J. I., Brahm, R., Petrovich, C., Jordán, A., Henning, T., Trifonov, T., Winn, J. N., Rea, E., Günther, M. N., Agabi, A., Bendjoya, P., Bhaskar, H., Bouchy, F., Catelan, M., Charalambous, C., Deloupy, V., Dransfield, G., Eberhardt, J., Espinoza, N., ... Ziegler, C. (2026). A Cold and Superpuffy Planet on a Prograde Orbit. Astrophysical Journal Letters, 996(1), Article L13. https://doi.org/10.3847/2041-8213/ae2bfa

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title = "A Cold and Superpuffy Planet on a Prograde Orbit",

abstract = "We report the discovery of TOI-4507 b, a transiting sub-Saturn with a density <0.2 g cm−3 on a 105 days prograde orbit around a 700 Myr old F star. The transits were detected using data from TESS as well as the Antarctic telescope ASTEP. A joint analysis of the light curves and radial velocities from HARPS, FEROS, and CORALIE confirmed the planetary nature of the signal, by limiting the mass to be below 20 M⊕ at 95\% confidence. The radial velocities also exhibit the Rossiter–McLaughlin effect and imply that the planet orbits the star in a prograde orbit with a sky-projected obliquity λ = −15+50−44° (∣λ∣ < 80° at 3σ). With these characteristics, TOI-4507 is one of the longest-period systems for which the stellar obliquity has been measured, and the planet is among the longest-period and youngest “superpuff” planets yet discovered.",

keywords = "Transit photometry, Exoplanets, Cold Neptunes, Radial velocity",

author = "Espinoza-Retamal, \{Juan I.\} and Rafael Brahm and Cristobal Petrovich and Andr{\'e}s Jord{\'a}n and Thomas Henning and Trifon Trifonov and Winn, \{Joshua N.\} and Erika Rea and G{\"u}nther, \{Maximilian N.\} and Abdelkrim Agabi and Philippe Bendjoya and Hareesh Bhaskar and Fran{\c c}ois Bouchy and M{\'a}rcio Catelan and Carolina Charalambous and Vincent Deloupy and George Dransfield and Jan Eberhardt and N{\'e}stor Espinoza and Freckelton, \{Alix V.\} and Tristan Guillot and Hobson, \{Melissa J.\} and Jones, \{Mat{\'i}as I.\} and Monika Lendl and Djamel Mekarnia and Mu{\~n}oz, \{Diego J.\} and \{D. Nielsen\}, Louise and Rojas, \{Felipe I.\} and Fran{\c c}ois-Xavier Schmider and Elyar Sedaghati and Gu{\d}mundur Stef{\'a}nsson and Stephanie Striegel and Olga Suarez and \{Tala Pinto\}, Marcelo and Mathilde Timmermans and Triaud, \{Amaury H. M. J.\} and St{\'e}phane Udry and Sol{\`e}ne Ulmer-Moll and Carl Ziegler",

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doi = "10.3847/2041-8213/ae2bfa",

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Espinoza-Retamal, JI, Brahm, R, Petrovich, C, Jordán, A, Henning, T, Trifonov, T, Winn, JN, Rea, E, Günther, MN, Agabi, A, Bendjoya, P, Bhaskar, H, Bouchy, F, Catelan, M, Charalambous, C, Deloupy, V, Dransfield, G, Eberhardt, J, Espinoza, N, Freckelton, AV, Guillot, T, Hobson, MJ, Jones, MI, Lendl, M, Mekarnia, D, Muñoz, DJ, D. Nielsen, L, Rojas, FI, Schmider, F-X, Sedaghati, E, Stefánsson, G, Striegel, S, Suarez, O, Tala Pinto, M, Timmermans, M , Triaud, AHMJ, Udry, S, Ulmer-Moll, S & Ziegler, C 2026, 'A Cold and Superpuffy Planet on a Prograde Orbit', Astrophysical Journal Letters, vol. 996, no. 1, L13. https://doi.org/10.3847/2041-8213/ae2bfa

TY - JOUR

T1 - A Cold and Superpuffy Planet on a Prograde Orbit

AU - Espinoza-Retamal, Juan I.

AU - Brahm, Rafael

AU - Petrovich, Cristobal

AU - Jordán, Andrés

AU - Henning, Thomas

AU - Trifonov, Trifon

AU - Winn, Joshua N.

AU - Rea, Erika

AU - Günther, Maximilian N.

AU - Agabi, Abdelkrim

AU - Bendjoya, Philippe

AU - Bhaskar, Hareesh

AU - Bouchy, François

AU - Catelan, Márcio

AU - Charalambous, Carolina

AU - Deloupy, Vincent

AU - Dransfield, George

AU - Eberhardt, Jan

AU - Espinoza, Néstor

AU - Freckelton, Alix V.

AU - Guillot, Tristan

AU - Hobson, Melissa J.

AU - Jones, Matías I.

AU - Lendl, Monika

AU - Mekarnia, Djamel

AU - Muñoz, Diego J.

AU - D. Nielsen, Louise

AU - Rojas, Felipe I.

AU - Schmider, François-Xavier

AU - Sedaghati, Elyar

AU - Stefánsson, Guđmundur

AU - Striegel, Stephanie

AU - Suarez, Olga

AU - Tala Pinto, Marcelo

AU - Timmermans, Mathilde

AU - Triaud, Amaury H. M. J.

AU - Udry, Stéphane

AU - Ulmer-Moll, Solène

AU - Ziegler, Carl

PY - 2026/1/1

Y1 - 2026/1/1

N2 - We report the discovery of TOI-4507 b, a transiting sub-Saturn with a density <0.2 g cm−3 on a 105 days prograde orbit around a 700 Myr old F star. The transits were detected using data from TESS as well as the Antarctic telescope ASTEP. A joint analysis of the light curves and radial velocities from HARPS, FEROS, and CORALIE confirmed the planetary nature of the signal, by limiting the mass to be below 20 M⊕ at 95% confidence. The radial velocities also exhibit the Rossiter–McLaughlin effect and imply that the planet orbits the star in a prograde orbit with a sky-projected obliquity λ = −15+50−44° (∣λ∣ < 80° at 3σ). With these characteristics, TOI-4507 is one of the longest-period systems for which the stellar obliquity has been measured, and the planet is among the longest-period and youngest “superpuff” planets yet discovered.

AB - We report the discovery of TOI-4507 b, a transiting sub-Saturn with a density <0.2 g cm−3 on a 105 days prograde orbit around a 700 Myr old F star. The transits were detected using data from TESS as well as the Antarctic telescope ASTEP. A joint analysis of the light curves and radial velocities from HARPS, FEROS, and CORALIE confirmed the planetary nature of the signal, by limiting the mass to be below 20 M⊕ at 95% confidence. The radial velocities also exhibit the Rossiter–McLaughlin effect and imply that the planet orbits the star in a prograde orbit with a sky-projected obliquity λ = −15+50−44° (∣λ∣ < 80° at 3σ). With these characteristics, TOI-4507 is one of the longest-period systems for which the stellar obliquity has been measured, and the planet is among the longest-period and youngest “superpuff” planets yet discovered.

KW - Transit photometry

KW - Exoplanets

KW - Cold Neptunes

KW - Radial velocity

U2 - 10.3847/2041-8213/ae2bfa

DO - 10.3847/2041-8213/ae2bfa

M3 - Letter

SN - 2041-8205

VL - 996

JO - Astrophysical Journal Letters

JF - Astrophysical Journal Letters

IS - 1

M1 - L13

ER -

A Cold and Superpuffy Planet on a Prograde Orbit

Abstract

Keywords

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Projects

Temperate planets from Chile & Antarctica

An upgrade to the mount of the ASTEP telescope

H2020_ERC_BEBOP

Red-Enhanced Cameras to Seek Rocky Planets Transiting Ultra-Cool Dwarfs

Cite this