Six transiting planets and a chain of Laplace resonances in TOI-178
Journal article, 2021
Determining the architecture of multi-planetary systems is one of the cornerstones of understanding planet formation and evolution. Resonant systems are especially important as the fragility of their orbital configuration ensures that no significant scattering or collisional event has taken place since the earliest formation phase when the parent protoplanetary disc was still present. In this context, TOI-178 has been the subject of particular attention since the first TESS observations hinted at the possible presence of a near 2:3:3 resonant chain. Here we report the results of observations from CHEOPS, ESPRESSO, NGTS, and SPECULOOS with the aim of deciphering the peculiar orbital architecture of the system. We show that TOI-178 harbours at least six planets in the super-Earth to mini-Neptune regimes, with radii ranging from 1.152 to 2.87 Earth radii and periods of 1.91, 3.24, 6.56, 9.96, 15.23, and 20.71 days. All planets but the innermost one form a 2:4:6:9:12 chain of Laplace resonances, and the planetary densities show important variations from planet to planet, jumping from 1.02 to 0.177 times the Earth's density between planets c and d. Using Bayesian interior structure retrieval models, we show that the amount of gas in the planets does not vary in a monotonous way, contrary to what one would expect from simple formation and evolution models and unlike other known systems in a chain of Laplace resonances. The brightness of TOI-178 (H = 8.76 mag, J = 9.37 mag, V = 11.95 mag) allows for a precise characterisation of its orbital architecture as well as of the physical nature of the six presently known transiting planets it harbours. The peculiar orbital configuration and the diversity in average density among the planets in the system will enable the study of interior planetary structures and atmospheric evolution, providing important clues on the formation of super-Earths and mini-Neptunes. -0.070 -0.13 -0.23 -0.061 +0.073 +0.14 +0.28 +0.055
Techniques: Photometric
Celestial mechanics
Planets and satellites: Detection
Techniques: Spectroscopic
Planets and satellites: Dynamical evolution and stability
Author
A. Leleu
University of Geneva
Y. Alibert
University of Bern
N.C. Hara
University of Geneva
M.J. Hooton
University of Bern
T.G. Wilson
University of St Andrews
P. Robutel
Paris Observatory
J. B. Delisle
University of Geneva
J. Laskar
Paris Observatory
S. Hoyer
Laboratoire d'Astrophysique de Marseille
C. Lovis
University of Geneva
E. Bryant
The University of Warwick
E. Ducrot
University of Liège
J. Cabrera
German Aerospace Center (DLR)
L. Delrez
University of Geneva
J.S. Acton
University Of Leicester
V. Adibekyan
University of Porto
R. Allart
University of Geneva
C. Allende Prieto
Instituto de Astrofísica de Canarias
R. Alonso
Instituto de Astrofísica de Canarias
D. Alves
Camino El Observatorio 1515
D.R. Anderson
The University of Warwick
D. Angerhausen
Swiss Federal Institute of Technology in Zürich (ETH)
G. Anglada Escude´
Institute of Space Sciences (ICE) - CSIC
J. Asquier
European Space Research and Technology Centre (ESA ESTEC)
D. Barrado
European Space Astronomy Centre (ESAC)
S.C.C. Barros
University of Porto
W. Baumjohann
Institut fur Weltraumforschung
D. Bayliss
The University of Warwick
M. Beck
University of Geneva
T. Beck
University of Bern
A. Bekkelien
University of Geneva
W. Benz
University of Bern
N. Billot
University of Geneva
A. Bonfanti
Institut fur Weltraumforschung
X. Bonfils
Grenoble Alpes University
F. Bouchy
University of Geneva
V. Bourrier
University of Geneva
G. Boue´
Paris Observatory
A. Brandeker
Stockholm University
C. Broeg
University of Bern
M. Buder
German Aerospace Center (DLR)
A. Burdanov
University of Liège
Matt Burleigh
University Of Leicester
T. Bárczy
Admatis
A.C. Cameron
University of St Andrews
S. Chamberlain
University Of Leicester
S. Charnoz
Paris Descartes University
B. Cooke
The University of Warwick
C. Corral Van Damme
European Space Research and Technology Centre (ESA ESTEC)
A.C.M. Correia
Paris Observatory
S. Cristiani
Osservatorio Astronomico di Trieste
Mario Damasso
Istituto nazionale di astrofisica (INAF)
Melvyn B. Davies
Lund University
M. Deleuil
Laboratoire d'Astrophysique de Marseille
O. Demangeon
University of Porto
B.O. Demory
University of Bern
P. Di Marcantonio
Osservatorio Astronomico di Trieste
G. Di Persio
Istituto nazionale di astrofisica (INAF)
X. Dumusque
University of Geneva
D. Ehrenreich
University of Geneva
Anders Erikson
German Aerospace Center (DLR)
P. Figueira
University of Porto
A. Fortier
University of Bern
L. Fossati
Institut fur Weltraumforschung
Malcolm Fridlund
Leiden University
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
D. Futyan
University of Geneva
D. Gandolfi
University of Turin
A. Garcia´ Muno&tild;z
Technische Universität Berlin
L.J. Garcia
University of Liège
S. Gill
The University of Warwick
E. Gillen
Queen Mary University of London
Michaël Gillon
University of Liège
M.R. Goad
University Of Leicester
J.I. Gonza´lez Herna´ndez
Instituto de Astrofísica de Canarias
M. Guedel
University of Vienna
M.N. Gu¨nther
Massachusetts Institute of Technology (MIT)
J. Haldemann
University of Bern
B. Henderson
University Of Leicester
Kevin Heng
University of Bern
A.E. Hogan
University Of Leicester
K. Isaak
European Space Research and Technology Centre (ESA ESTEC)
Emmanuel Jehin
University of Liège
J.S. Jenkins
University of Chile (UCH)
A. Jorda´n
Adolfo Ibáñez University
L. Kiss
Hungarian Academy of Sciences
M. H. Kristiansen
Brorfelde Observatory
K. W.F. Lam
German Aerospace Center (DLR)
B. Lavie
University of Geneva
A. L. des Etangs
Institut d 'Astrophysique de Paris
M. Lendl
University of Geneva
J. Lillo-Box
European Space Astronomy Centre (ESAC)
G. Lo Curto
European Southern Observatory Santiago
D. Magrin
Istituto nazionale di astrofisica (INAF)
C.J.A.P. Martins
University of Porto
P. Maxted
Keele University
J. McCormac
The University of Warwick
A. Mehner
European Southern Observatory Santiago
G. Micela
Istituto nazionale di astrofisica (INAF)
P. Molaro
Osservatorio Astronomico di Trieste
M. Moyano
Universidad Catolica del Norte
C.A. Murray
University of Cambridge
Valerio Nascimbeni
Istituto nazionale di astrofisica (INAF)
N.J. Nunes
University of Lisbon
G. Olofsson
Stockholm University
H. P. Osborn
University of Bern
M. Oshagh
Instituto de Astrofísica de Canarias
R. Ottensamer
University of Vienna
I. Pagano
Istituto nazionale di astrofisica (INAF)
E. Palle
Instituto de Astrofísica de Canarias
P.P. Pedersen
University of Cambridge
Francesco Pepe
University of Geneva
Carina Persson
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
G. Peter
German Aerospace Center (DLR)
Giampaolo P. Piotto
Istituto nazionale di astrofisica (INAF)
G. Polenta
Agenzia Spaziale Italiana
Don L. Pollacco
The University of Warwick
E. Poretti
Istituto nazionale di astrofisica (INAF)
Francisco J. Pozuelos
University of Liège
D. Queloz
University of Geneva
Roberto Ragazzoni
Istituto nazionale di astrofisica (INAF)
N. Rando
European Space Research and Technology Centre (ESA ESTEC)
F. Ratti
European Space Research and Technology Centre (ESA ESTEC)
H. Rauer
German Aerospace Center (DLR)
L. Raynard
University Of Leicester
R. Rebolo
Instituto de Astrofísica de Canarias
C. Reimers
University of Vienna
I. Ribas
Institute of Space Sciences (ICE) - CSIC
N. C. Santos
University of Porto
Gaetano Scandariato
Istituto nazionale di astrofisica (INAF)
J. Schneider
Paris Observatory
D. Sebastian
University of Birmingham
M. Sestovic
University of Bern
A.E. Simon
University of Bern
Alexis M. S. Smith
German Aerospace Center (DLR)
S.G. Sousa
University of Porto
A. Sozzetti
Istituto nazionale di astrofisica (INAF)
Manfred B. Steller
Institut fur Weltraumforschung
A. Sua´rez Mascareno&tild;
Instituto de Astrofísica de Canarias
G.M. Szabó
Eötvös Loránd University (ELTE)
D. Segransan
University of Geneva
Nicolas Thomas
University of Bern
S. Thompson
University of Cambridge
R.H. Tilbrook
University Of Leicester
Amaury Triaud
University of Birmingham
O. Turner
University of Geneva
S. Udry
University of Geneva
V. Van Grootel
University of Liège
H. Venus
German Aerospace Center (DLR)
F. Verrecchia
Agenzia Spaziale Italiana
José I. Vines
Camino El Observatorio 1515
N. A. Walton
University of Cambridge
R.G. West
The University of Warwick
P.J. Wheatley
The University of Warwick
D. Wolter
German Aerospace Center (DLR)
M. Zapatero-Osorio
Centro de Astrobiologia (CAB)
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 649 A26Exoplanets from space -CHEOPS and PLATO ESA's next two projects (Phase 2)
Swedish National Space Board (65/19), 2020-01-01 -- 2022-12-31.
Swedish National Space Board (177/19), 2020-01-01 -- 2022-12-31.
Exoplanets from space – CHEOPS and PLATO, ESA’s next two projects
Swedish National Space Board (174/18), 2017-01-01 -- 2022-12-31.
Subject Categories
Astronomy, Astrophysics and Cosmology
Other Physics Topics
Embedded Systems
DOI
10.1051/0004-6361/202039767