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ABSTRACT Dwarf satellite galaxies are thought to be the remnants of the population of primordial structures that coalesced to form giant galaxies like the Milky Way1. It has previously been

suspected2 that dwarf galaxies may not be isotropically distributed around our Galaxy, because several are correlated with streams of H i emission, and may form coplanar groups3. These

suspicions are supported by recent analyses4,5,6,7. It has been claimed7 that the apparently planar distribution of satellites is not predicted within standard cosmology8, and cannot simply

represent a memory of past coherent accretion. However, other studies dispute this conclusion9,10,11. Here we report the existence of a planar subgroup of satellites in the Andromeda galaxy

(M 31), comprising about half of the population. The structure is at least 400 kiloparsecs in diameter, but also extremely thin, with a perpendicular scatter of less than 14.1 kiloparsecs.

Radial velocity measurements12,13,14,15 reveal that the satellites in this structure have the same sense of rotation about their host. This shows conclusively that substantial numbers of

dwarf satellite galaxies share the same dynamical orbital properties and direction of angular momentum. Intriguingly, the plane we identify is approximately aligned with the pole of the

Milky Way’s disk and with the vector between the Milky Way and Andromeda. Access through your institution Buy or subscribe This is a preview of subscription content, access via your

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* Learn about institutional subscriptions * Read our FAQs * Contact customer support SIMILAR CONTENT BEING VIEWED BY OTHERS ANDROMEDA’S ASYMMETRIC SATELLITE SYSTEM AS A CHALLENGE TO COLD

DARK MATTER COSMOLOGY Article Open access 11 April 2025 THE MILKY WAY’S PLANE OF SATELLITES IS CONSISTENT WITH _Λ_CDM Article Open access 19 December 2022 AN EVOLUTIONARY CONTINUUM FROM

NUCLEATED DWARF GALAXIES TO STAR CLUSTERS Article 08 November 2023 REFERENCES * Klypin, A., Kravtsov, A. V., Valenzuela, O. & Prada, F. Where are the missing galactic satellites?

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ACKNOWLEDGEMENTS We thank the staff of the Canada-France-Hawaii Telescope for taking the PAndAS data, and for their continued support throughout the project. We thank one of our referees, B.

Tully, for pointing out that IC 1613 could also be associated to the planar structure. R.A.I. and D.V.G. gratefully acknowledge support from the Agence Nationale de la Recherche though the

grant POMMME, and would like to thank B. Famaey for discussions. G.F.L. thanks the Australian Research Council for support through his Future Fellowship and Discovery Project. This work is

based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada–France–Hawaii Telescope, which is operated by the National Research Council (NRC)

of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. Some of the data presented

here were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National

Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. AUTHOR INFORMATION AUTHORS AND AFFILIATIONS *

Observatoire Astronomique de Strasbourg, 11 rue de l’Université, F-67000 Strasbourg, France , Rodrigo A. Ibata & Nicolas F. Martin * Sydney Institute for Astronomy, School of Physics,

A28, The University of Sydney, New South Wales, 2006, Australia Geraint F. Lewis * Department of Physics and Astronomy, Macquarie University, New South Wales, 2109, Australia Anthony R. Conn

* Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK , Michael J. Irwin * NRC Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria,

British Columbia, V9E 2E7, Canada , Alan W. McConnachie * Department of Physics and Atmospheric Science, Dalhousie University, 6310 Coburg Road, Halifax, Nova Scotia, B3H 4R2, Canada, Scott

C. Chapman * Max-Planck-Institut für Astronomie, Königstuhl 17, Heidelberg, 69117, Germany Michelle L. Collins & Nicolas F. Martin * Department of Astronomy, University of Massachusetts,

LGRT 619-E, 710 North Pleasant Street, Amherst, Massachusetts 01003-9305, USA, Mark Fardal * Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh

EH9 3HJ, UK , Annette M. N. Ferguson * Lycée International des Pontonniers, 1 rue des Pontonniers, F-67000 Strasbourg, France , Neil G. Ibata * The Australian National University, Mount

Stromlo Observatory, Cotter Road, Weston Creek, Australian Capital Province 2611, Australia , A. Dougal Mackey * Department of Physics and Astronomy, University of Victoria, 3800 Finnerty

Road, Victoria, British Columbia, V8P 5C2, Canada, Julio Navarro * Department of Physics and Astronomy, University of California, Los Angeles, PAB, 430 Portola Plaza, Los Angeles, California

90095-1547, USA, R. Michael Rich * LERMA, UMR CNRS 8112, Observatoire de Paris, 61 Avenue de l’Observatoire, 75014 Paris, France , David Valls-Gabaud * Department of Physics, Engineering

Physics, and Astronomy, Queen’s University, Kingston, Ontario, K7L 3N, Canada, Lawrence M. Widrow Authors * Rodrigo A. Ibata View author publications You can also search for this author

inPubMed Google Scholar * Geraint F. Lewis View author publications You can also search for this author inPubMed Google Scholar * Anthony R. Conn View author publications You can also search

for this author inPubMed Google Scholar * Michael J. Irwin View author publications You can also search for this author inPubMed Google Scholar * Alan W. McConnachie View author

publications You can also search for this author inPubMed Google Scholar * Scott C. Chapman View author publications You can also search for this author inPubMed Google Scholar * Michelle L.

Collins View author publications You can also search for this author inPubMed Google Scholar * Mark Fardal View author publications You can also search for this author inPubMed Google

Scholar * Annette M. N. Ferguson View author publications You can also search for this author inPubMed Google Scholar * Neil G. Ibata View author publications You can also search for this

author inPubMed Google Scholar * A. Dougal Mackey View author publications You can also search for this author inPubMed Google Scholar * Nicolas F. Martin View author publications You can

also search for this author inPubMed Google Scholar * Julio Navarro View author publications You can also search for this author inPubMed Google Scholar * R. Michael Rich View author

publications You can also search for this author inPubMed Google Scholar * David Valls-Gabaud View author publications You can also search for this author inPubMed Google Scholar * Lawrence

M. Widrow View author publications You can also search for this author inPubMed Google Scholar CONTRIBUTIONS All authors assisted in the development and writing of the paper. In addition,

the structural and kinematic properties of the dwarf population, and the significance of the Andromeda plane were determined by R.A.I., G.F.L. and A.R.C., based on distances determined by

the same group (as part of the PhD research of A.R.C.). In addition, A.W.M. is the Principal Investigator of PAndAS; M.J.I. and R.A.I. led the data processing effort; R.A.I. was the

Principal Investigator of an earlier CFHT MegaPrime/MegaCam survey, which PAndAS builds on (which included S.C.C., A.M.N.F., M.J.I., G.F.L., N.F.M. and A.W.M.). R.M.R. is Principal

Investigator of the spectroscopic follow-up with the Keck Telescope. M.L.C. and S.C.C. led the analysis of the kinematic determination of the dwarf population, and N.F.M. led the detection

of the dwarf population from PAndAS data. N.G.I. performed the initial analysis of the satellite kinematics. CORRESPONDING AUTHOR Correspondence to Rodrigo A. Ibata. ETHICS DECLARATIONS

COMPETING INTERESTS The authors declare no competing financial interests. SUPPLEMENTARY INFORMATION SUPPLEMENTARY INFORMATION This file contains Supplementary Text 1-2, Supplementary Figure

1 and a Supplementary Reference. (PDF 126 kb) POWERPOINT SLIDES POWERPOINT SLIDE FOR FIG. 1 POWERPOINT SLIDE FOR FIG. 2 POWERPOINT SLIDE FOR FIG. 3 RIGHTS AND PERMISSIONS Reprints and

permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Ibata, R., Lewis, G., Conn, A. _et al._ A vast, thin plane of corotating dwarf galaxies orbiting the Andromeda galaxy. _Nature_ 493, 62–65

(2013). https://doi.org/10.1038/nature11717 Download citation * Received: 18 September 2012 * Accepted: 23 October 2012 * Published: 02 January 2013 * Issue Date: 03 January 2013 * DOI:

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