An eccentric massive protobinary assembled via a core-merger parabolic encounter
Journal article, 2026
Most massive stars form in binary systems, which profoundly influence their subsequent evolution. However, how such systems form remains poorly understood, with several competing scenarios proposed, including disk fragmentation, core fragmentation and capture. Determining the orbital architectures of massive binaries, particularly during their earliest embedded phases, is, therefore, crucial for distinguishing among these formation pathways, but direct measurements of their three-dimensional motions have remained exceptionally challenging. Here we present high-resolution, multi-epoch submillimetre-to-centimetre ALMA and JVLA observations of the massive protobinary IRAS 07299−1651, complemented by JWST and VLT infrared imaging. We detect the orbital proper motion of the binary components, enabling a full three-dimensional orbital reconstruction. Combining orbital fitting, multi-wavelength continuum modelling, hydrogen recombination line kinematics and jet observations, we find that the preferred orbital solutions are highly eccentric and close to parabolic, and both circumstellar disks are strongly misaligned with the orbital plane. These properties are naturally explained by a ‘core-merger’ scenario in which the two protostars originated independently from initially unbound cores that recently underwent a near-parabolic encounter, producing an eccentric binary with a current separation of about 200 au. These findings suggest that the core-merger process may represent an important pathway for forming eccentric massive binaries.
Author
Yao Wang
Shanghai Jiao Tong University
Yichen Zhang
Shanghai Jiao Tong University
R. Fedriani
Spanish National Research Council (CSIC)
Kei E.I. Tanaka
Institute of Science Tokyo
Viviana Rosero
California Institute of Technology (Caltech)
Space Science Institute
Kai Yang
Shanghai Jiao Tong University
Morten Andersen
European Southern Observatory (ESO)
M. T. Beltrán
Arcetri Astrophysical Observatory
Mélisse Bonfand
University of Virginia
Yu Cheng
National Astronomical Observatory of Japan
James M. De Buizer
SETI Institute
Yihuan Di
Shanghai Jiao Tong University
Garay Guido
Chinese Academy of Sciences
University of Chile (UCH)
Prasanta Gorai
University of Oslo
Heidelberg University
Z. Y. Li
University of Virginia
Yao-Lun Yang
RIKEN
Jonathan Tan
University of Virginia
Chalmers, Physics, Subatomic, High Energy and Plasma Physics
Nature Astronomy
23973366 (eISSN)
Vol. In PressSubject Categories (SSIF 2025)
Atom and Molecular Physics and Optics
Astronomy, Astrophysics, and Cosmology
DOI
10.1038/s41550-026-02953-z