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Age dating of an early Milky Way merger via asteroseismology of the naked-eye star ν Indi

J. Chaplin, William; M. Serenelli, Aldo; Miglio, Andrea; Morel, Thierry; Mackereth, J. Ted; Vincenzo, Fiorenzo; Kjeldsen Sarbani Basu, Hans; H. Ball, Warrick; Stokholm, Amalie; Verma, Kuldeep; Rørsted Mosumgaard, Jakob; Silva Aguirre, Victor; Mazumdar, Anwesh; Ranadive, Pritesh; M. Antia, H.; Lebreton, Yveline; Ong, Joel; Appourchaux, Thierry; R. Bedding, Timothy; Christensen-Dalsgaard, Jørgen; Creevey, Orlagh; A. García, Rafael; Handberg, Rasmus; Huber, Daniel; D. Kawaler, Steven; N. Lund, Mikkel; S. Metcalfe, Travis; G. Stassun, Keivan; Bazot, Michäel; Beck, Paul; J. Bell, Keaton; Bergemann, Maria; L. Buzasi, Derek; Benomar, Othman; Bossini, Diego; Bugnet, Lisa; L. Campante, Tiago; Çelik Orhan, Zeynep; Corsaro, Enrico; González-Cuesta, Lucía; R. Davies, Guy; Pia Di Mauro, Maria; Egeland, Ricky; P. Elsworth, Yvonne; Gaulme, Patrick; Ghasemi, Hamed; Guo, Zhao; J. Hall, Oliver; Hasanzadeh, Amir; Hekker, Saskia; Howe, Rachel; M. Jenkins, Jon; Jiménez, Antonio; Kiefer, René; S. Kuszlewicz...

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William J. Chaplin

Aldo M. Serenelli

Andrea Miglio

Thierry Morel

J. Ted Mackereth

Fiorenzo Vincenzo

Hans Kjeldsen Sarbani Basu

Warrick H. Ball

Amalie Stokholm

Kuldeep Verma

Jakob Rørsted Mosumgaard

Victor Silva Aguirre

Anwesh Mazumdar

Pritesh Ranadive

H. M. Antia

Yveline Lebreton

Joel Ong

Thierry Appourchaux

Timothy R. Bedding

Jørgen Christensen-Dalsgaard

Orlagh Creevey

Rafael A. García

Rasmus Handberg

Daniel Huber

Steven D. Kawaler

Mikkel N. Lund

Travis S. Metcalfe

Keivan G. Stassun

Michäel Bazot

Paul Beck

Keaton J. Bell

Maria Bergemann

Derek L. Buzasi

Othman Benomar

Diego Bossini

Lisa Bugnet

Tiago L. Campante

Zeynep Çelik Orhan

Enrico Corsaro

Lucía González-Cuesta

Guy R. Davies

Maria Pia Di Mauro

Ricky Egeland

Yvonne P. Elsworth

Patrick Gaulme

Hamed Ghasemi

Zhao Guo

Oliver J. Hall

Amir Hasanzadeh

Saskia Hekker

Rachel Howe

Jon M. Jenkins

Antonio Jiménez

René Kiefer

James S. Kuszlewicz

Thomas Kallinger

David W. Latham

Mia S. Lundkvist

Savita Mathur

Josefina Montalbán

Benoit Mosser

Andres Moya Bedón

Martin Bo Nielsen

Sibel Örtel

Ben M. Rendle

George R. Ricker

Thaíse S. Rodrigues

Ian W. Roxburgh

Hossein Safari

Mathew Schofield

Sara Seager

Dennis Stello

Róbert Szabó

Jamie Tayar

Nathalie Themeßl

Alexandra E. L. Thomas

Roland K. Vanderspek

Walter E. van Rossem

Mathieu Vrard

Achim Weiss

Timothy R. White

Joshua N. Winn

Mutlu Yıldız


Over the course of its history, the Milky Way has ingested multiple smaller satellite galaxies. While these accreted stellar populations can be forensically identified as kinematically distinct structures within the Galaxy, it is difficult in general to precisely date the age at which any one merger occurred. Recent results have revealed a population of stars that were accreted via the collision of a dwarf galaxy, called \textit{Gaia}-Enceladus, leading to a substantial pollution of the chemical and dynamical properties of the Milky Way. Here, we identify the very bright, naked-eye star $\nu$\,Indi as a probe of the age of the early in situ population of the Galaxy. We combine asteroseismic, spectroscopic, astrometric, and kinematic observations to show that this metal-poor, alpha-element-rich star was an indigenous member of the halo, and we measure its age to be $11.0 \pm 0.7$ (stat) $\pm 0.8$ (sys)$\,\rm Gyr$. The star bears hallmarks consistent with it having been kinematically heated by the \textit{Gaia}-Enceladus collision. Its age implies that the earliest the merger could have begun was 11.6 and 13.2 Gyr ago at 68 and 95% confidence, respectively. Input from computations based on hierarchical cosmological models tightens (i.e. reduces) slightly the above limits.

Journal Article Type Letter
Acceptance Date Nov 13, 2020
Publication Date Jan 13, 2020
Publicly Available Date May 26, 2023
Journal Nature Astronomy
Print ISSN 2397-3366
Publisher Nature Research
Peer Reviewed Peer Reviewed
Keywords Astrophysics of Galaxies; Solar and Stellar Astrophysics
Publisher URL


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