Multiplicity Study of Exoplanet Host Stars


The team | Latest resultsOur current Projects | Our Publications | Student Thesis Work | Press Releases


A key aspect in the diversity of exoplanets is the multiplicity of their host stars.

As described by theories stellar companions of exoplanet host stars can significantly influence the formation process of planets around these stars as well as the long-term evolution of their orbits. On the one hand, in close binary systems, planet formation and long-term stable orbits of planets are restricted to the close vicinity (only a few astronomical units) around the host stars. On the other hand, in wide binary systems, the orbital evolution of the star system itself, for example under the influence of galactic tides or perturbations from other passing stars, can significantly affect the orbits of exoplanets around their host stars.

How planets form and evolve in multiple star systems is a very important question in modern astrophysics, since a large fraction of the stars in our galaxy are members of binary or even higher order multiple star systems. Furthermore, the efficiency of planet formation in these systems also affects the total number of planets in the Milky Way.

In order to detect such stellar systems with exoplanets, we have initiated several surveys to search for stellar companions of exoplanet host stars, using either seeing-limited, lucky-, or high-contrast adaptive optics imaging, as well as data releases of the European Space Agency (ESA) Gaia mission. With these different surveys, we are able to cover the entire detection space for possible stellar companions around the exoplanet host stars and can thus accurately determine the multiplicity rate of these stars, and characterize the properties of their companions. Eventually, our efforts will allow us to determine the true impact of stellar multiplicity on planet formation and evolution.

Latest Results:

The Impact of stellar Multiplicity on Planet Formation and Evolution


Left Figure: Cumulative mass distribution function of single (grey line) and multiple star planets (dark line). The mass regime of super-Earths and (super-)Jovian exoplanets is indicated by red dashed vertical lines. Super-Earth are more often found in single star systems compared to (super-)Jovian exoplanets. In multiple star systems (super-Jovian) exoplanets are more common than around single stars.

Middle Figure: Distribution of the mass of multiple star planets with respect to the gravitational perturbation of the companion star(s). The blue lines show the median mass of the exoplanets in the corresponding range of gravitational perturbation.

Right Figure: Distribution of the orbital eccentricity of multiple star planets versus the gravitational perturbation of the companion star(s). The blue lines show the median orbital eccentricity of the exoplanets in the corresponding range of gravitational perturbation.

Reference: Michel, K.-U. & Mugrauer, M. (2024) "Gaia Search for (sub)stellar companions of exoplanet hosts" MNRAS 527, 3183


Search for Stellar Companions of Exoplanet Host Stars with AstraLux/CAHA 2.2 m


Figure: AstraLux I-band images of exoplanet host stars (located in the center of each image) with detected co-moving stellar companions.

Reference: Schlagenhauf et al. (2024) "Search for Stellar Companions of Exoplanet Host Stars with AstraLux/CAHA 2.2 m" MNRAS 529, 4768

The team

Principle Investigator:

Team Members:

  • Christian Adam (Centro de Astronomía de la Universidad de Antofagasta)
  • Lara Dürrenberg (FSU Jena)

  • Matilde Fernández Hernández (IAA-CSIC)

  • Christian Ginski (Anton Pannekoek Institute for Astronomy)

  • Ann-Kathrin Kollak (AIU Jena)
  • Kai-Uwe Michel (AIU Jena)
  • Ralph Neuhäuser (AIU Jena)

  • Saskia Schlagenhauf (AIU Jena)

  • Nikolaus Vogt (Universidad de Valparaíso)

Former Team Members:

  • Sven Buder
  • Therese Heyne

  • Tsevi Mazeh
  • Friedemann Reum

  • Tristan Röll

  • Johanna Rück
  • Martin Seeliger

  • Andreas Seifahrt

  • Jule Zander

Our current Projects

  • Long-term Multiplicity Survey of northern Exoplanet host Stars with the Lucky-Imager AstraLux at CAHA/2.2m (started in 2008)

    → for results see publications below
  • Long-term Multiplicity Survey of southern Exoplanet host Stars using the extreme Adaptive Optics SPHERE/VLT (started in 2016)

    → for results see publications below
  • Multiplicity Study of Exoplanet Hosts using Data of the ESA-Gaia mission (started in 2018)

    → for results see publications below & VizieR catalogues of detected companions (Link1, Link2, Link3)

  • ESA-Gaia Search for stellar companions of TESS Objects of Interest (started in 2020)

    → for results see publications below & VizieR catalogues of detected companions (Link1, Link2, Link3, Link4) & Our online image library of detected companions

Our Publications

Student Thesis Work

  • Lara Dürrenberg: "Suche und Charakterisierung stellarer Begleiter von KOIs"
  • Ann-Kathrin Kollak: "Suche nach stellaren Begleitern von (C)TOIs"
  • Kai-Uwe Michel: "Search for (sub)stellar Companions of Exoplanet Hosts by using Data from the ESA-Gaia mission"
  • Johanna Rück: "Suche nach stellaren Begleitern potentieller Planeten-Muttersterne"
  • Saskia Schlagenhauf: "AstraLux Lucky-Imaging Observations of Exoplanet host Stars

  • Jule Zander: "ESA-Gaia Search for stellar Companions of TESS Objects of Interest"

Press Releases