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

Planets and satellites: Detection

Techniques: Spectroscopic

Techniques: Photometric

Planets and satellites: Dynamical evolution and stability

Celestial mechanics

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 Astrofisico de Canarias

R. Alonso

Instituto Astrofisico 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 Astrofisico 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

Osservatorio Astronomico di Padova

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

Osservatorio Astronomico di Padova

N.J. Nunes

University of Lisbon

G. Olofsson

Stockholm University

H. P. Osborn

University of Bern

M. Oshagh

Instituto Astrofisico de Canarias

R. Ottensamer

University of Vienna

I. Pagano

Osservatorio Astrofisico di Catania

E. Palle

Instituto Astrofisico 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

Osservatorio Astronomico di Padova

G. Polenta

ASI

Don L. Pollacco

The University of Warwick

E. Poretti

INAF (Telescopio Nazionale Galileo)

Francisco J. Pozuelos

University of Liège

D. Queloz

University of Geneva

Roberto Ragazzoni

Osservatorio Astronomico di Padova

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 Astrofisico de Canarias

C. Reimers

University of Vienna

I. Ribas

Institute of Space Sciences (ICE) - CSIC

N. C. Santos

University of Porto

Gaetano Scandariato

Osservatorio Astrofisico di Catania

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 Astrofisico 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

ASI

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 A26

Exoplanets from space – CHEOPS and PLATO, ESA’s next two projects

Swedish National Space Board (174/18), 2017-01-01 -- 2022-12-31.

Exoplanets from space -CHEOPS and PLATO ESA's next two projects (Phase 2)

Swedish National Space Board (177/19), 2020-01-01 -- 2022-12-31.

Swedish National Space Board (65/19), 2020-01-01 -- 2022-12-31.

Subject Categories

Astronomy, Astrophysics and Cosmology

Other Physics Topics

Embedded Systems

DOI

10.1051/0004-6361/202039767

More information

Latest update

9/13/2021