CHEOPS geometric albedo of the hot Jupiter HD 209458 b
Journal article, 2022

We report the detection of the secondary eclipse of the hot Jupiter HD 209458 b in optical/visible light using the CHEOPS space telescope. Our measurement of 20.4+3.2-3.3 parts per million translates into a geometric albedo of Ag = 0.096 ± 0.016. The previously estimated dayside temperature of about 1500 K implies that our geometric albedo measurement consists predominantly of reflected starlight and is largely uncontaminated by thermal emission. This makes the present result one of the most robust measurements of Ag for any exoplanet. Our calculations of the bandpass-integrated geometric albedo demonstrate that the measured value of Ag is consistent with a cloud-free atmosphere, where starlight is reflected via Rayleigh scattering by hydrogen molecules, and the water and sodium abundances are consistent with stellar metallicity. We predict that the bandpass-integrated TESS geometric albedo is too faint to detect and that a phase curve of HD 209458 b observed by CHEOPS would have a distinct shape associated with Rayleigh scattering if the atmosphere is indeed cloud free.

Planetary systems

Planets and satellites: Atmospheres

Planets

Techniques: Photometric

Satellites: Individual: HD 209458 b

Author

A. Brandeker

Stockholm University

Kevin Heng

The University of Warwick

University of Bern

M. Lendl

University of Geneva

J. A. Patel

Stockholm University

Brett M. Morris

University of Bern

C. Broeg

University of Bern

P. Guterman

Laboratoire d'Astrophysique de Marseille

Division Technique INSU

M. Beck

University of Geneva

P. Maxted

Keele University

O. Demangeon

University of Porto

L. Delrez

University of Liège

B.O. Demory

University of Bern

D. Kitzmann

University of Bern

N. C. Santos

University of Porto

V. Singh

Istituto nazionale di astrofisica (INAF)

Y. Alibert

University of Bern

R. Alonso

Instituto de Astrofísica de Canarias

University of La Laguna

G. Anglada

Spanish National Research Council (CSIC)

Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)

T. Bárczy

Admatis

D. Barrado

Centro de Astrobiologia (CAB)

S.C.C. Barros

University of Porto

W. Baumjohann

Institut fur Weltraumforschung

T. Beck

University of Bern

W. Benz

University of Bern

N. Billot

University of Geneva

X. Bonfils

Grenoble Alpes University

G. Bruno

University of Bern

J. Cabrera

German Aerospace Center (DLR)

S. Charnoz

Paris Descartes University

A. Collier Cameron

University of St Andrews

C. Corral Van Damme

European Space Research and Technology Centre (ESA ESTEC)

Szilard Csizmadia

German Aerospace Center (DLR)

M. B. Davies

Lund University

M. Deleuil

Laboratoire d'Astrophysique de Marseille

A. Deline

University of Geneva

D. Ehrenreich

University of Geneva

Anders Erikson

German Aerospace Center (DLR)

J. Farinato

Istituto nazionale di astrofisica (INAF)

A. Fortier

University of Bern

L. Fossati

Institut fur Weltraumforschung

Malcolm Fridlund

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Leiden University

D. Gandolfi

University of Turin

Michaël Gillon

University of Liège

M. Gudel

University of Vienna

S. Hoyer

Laboratoire d'Astrophysique de Marseille

K. Isaak

European Space Research and Technology Centre (ESA ESTEC)

L.L. Kiss

Hungarian Academy of Sciences

Eötvös Loránd University (ELTE)

J. Laskar

Paris Observatory

A. L. des Etangs

Institut d 'Astrophysique de Paris

C. Lovis

University of Geneva

A. Luntzer

University of Vienna

D. Magrin

Istituto nazionale di astrofisica (INAF)

Valerio Nascimbeni

Istituto nazionale di astrofisica (INAF)

G. Olofsson

Stockholm University

R. Ottensamer

University of Vienna

I. Pagano

Istituto nazionale di astrofisica (INAF)

Enric Palle

Instituto de Astrofísica de Canarias

G. Peter

German Aerospace Center (DLR)

Giampaolo P. Piotto

Istituto nazionale di astrofisica (INAF)

University of Padua

Don L. Pollacco

The University of Warwick

D. Queloz

University of Cambridge

Swiss Federal Institute of Technology in Zürich (ETH)

Roberto Ragazzoni

Istituto nazionale di astrofisica (INAF)

University of Padua

N. Rando

European Space Research and Technology Centre (ESA ESTEC)

H. Rauer

Technische Universität Berlin

German Aerospace Center (DLR)

Freie Universität Berlin

I. Ribas

Spanish National Research Council (CSIC)

Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)

Gaetano Scandariato

Istituto nazionale di astrofisica (INAF)

D. Segransan

University of Geneva

A.E. Simon

University of Bern

Alexis M. S. Smith

German Aerospace Center (DLR)

S. G. Sousa

University of Porto

Manfred B. Steller

Institut fur Weltraumforschung

G.M. Szabó

Eötvös Loránd University (ELTE)

Nicolas Thomas

University of Bern

S. Udry

University of Geneva

V. Van Grootel

University of Liège

N. A. Walton

University of Cambridge

D. Wolter

German Aerospace Center (DLR)

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 659 L4

Subject Categories (SSIF 2011)

Astronomy, Astrophysics and Cosmology

DOI

10.1051/0004-6361/202243082

More information

Latest update

3/9/2025 1