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Discovery of a directly imaged planet to the young solar analog YSES 2

Bohn, Alexander J. and Ginski, Christian and Kenworthy, Matthew A. and Mamajek, Eric E. and Pecaut, Mark J. and Mugrauer, Markus and Vogt, Nikolaus and Adam, Christian and Meshkat, Tiffany and Reggiani, Maddalena and Snik, Frans (2021) Discovery of a directly imaged planet to the young solar analog YSES 2. Astronomy and Astrophysics, 648 . Art. No. A73. ISSN 0004-6361.

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Context. To understand the origin and formation pathway of wide-orbit gas giant planets, it is necessary to expand the limited sample of these objects. The mass of exoplanets derived with spectrophotometry, however, varies strongly as a function of the age of the system and the mass of the primary star. Aims. By selecting stars with similar ages and masses, the Young Suns Exoplanet Survey (YSES) aims to detect and characterize planetary-mass companions to solar-type host stars in the Scorpius-Centaurus association. Methods. Our survey is carried out with VLT/SPHERE with short exposure sequences on the order of 5 min per star per filter. The subtraction of the stellar point spread function (PSF) is based on reference star differential imaging using the other targets (with similar colors and magnitudes) in the survey in combination with principal component analysis. Two astrometric epochs that are separated by more than one year are used to confirm co-moving companions by proper motion analysis. Results. We report the discovery of YSES 2b, a co-moving, planetary-mass companion to the K1 star YSES 2 (TYC 8984-2245-1, 2MASS J11275535-6626046). The primary has a Gaia EDR3 distance of 110 pc, and we derive a revised mass of 1.1 M_⊙ and an age of approximately 14 Myr. We detect the companion in two observing epochs southwest of the star at a position angle of 205° and with a separation of ~1."05, which translates to a minimum physical separation of 115 au at the distance of the system. Photometric measurements in the H and K_s bands are indicative of a late L spectral type, similar to the innermost planets around HR 8799. We derive a photometric planet mass of 6.3_(−0.9)^(+1.6) M_(Jup) using AMES-COND and AMES-dusty evolutionary models; this mass corresponds to a mass ratio of q = (0.5 ± 0.1)% with the primary. This is the lowest mass ratio of a direct imaging planet around a solar-type star to date. We discuss potential formation mechanisms and find that the current position of the planet is compatible with formation by disk gravitational instability, but its mass is lower than expected from numerical simulations. Formation via core accretion must have occurred closer to the star, yet we do not find evidence that supports the required outward migration, such as via scattering off another undiscovered companion in the system. We can exclude additional companions with masses greater than 13 M_(Jup) in the full field of view of the detector (0."15<ρ<5."50), at 0."5 we can rule out further objects that are more massive than 6 M_(Jup), and for projected separations ρ >2" we are sensitive to planets with masses as low as 2 M_(Jup). Conclusions. YSES 2b is an ideal target for follow-up observations to further the understanding of the physical and chemical formation mechanisms of wide-orbit Jovian planets. The YSES strategy of short snapshot observations (≤5 min) and PSF subtraction based on a large reference library proves to be extremely efficient and should be considered for future direct imaging surveys.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper ItemData
Bohn, Alexander J.0000-0003-1401-9952
Kenworthy, Matthew A.0000-0002-7064-8270
Mamajek, Eric E.0000-0003-2008-1488
Pecaut, Mark J.0000-0002-7859-1504
Meshkat, Tiffany0000-0001-6126-2467
Reggiani, Maddalena0000-0003-2911-0898
Snik, Frans0000-0003-1946-7009
Additional Information:© ESO 2021. Received 6 February 2021 / Accepted 17 March 2021. Data are only available at the CDS via anonymous ftp to ( or via Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programs 099.C-0698(A), 0101.C-0153(A), 0101.C-0341(A), and 106.20X2.001. We would like to thank the anonymous referee for the very valuable feedback that helped improving the quality of the manuscript. Especially, the extremely kind way of providing this feedback was highly appreciated by the authors. The research of A.J.B. and F.S. leading to these results has received funding from the European Research Council under ERC Starting Grant agreement 678194 (FALCONER). Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). M.M. would like to thank the German Research Foundation (DFG) for support in the program MU 2695/27-1. M.R. acknowledges support from the FWO research program under project 1280121N. This research has used the SIMBAD database, operated at CDS, Strasbourg, France (Wenger et al. 2000). This work has used data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This publication makes use of VOSA, developed under the Spanish Virtual Observatory project supported by the Spanish MINECO through grant AyA2017-84089. To achieve the scientific results presented in this article we made use of the Python programming language (Python Software Foundation,, especially the SciPy (Virtanen et al. 2020), NumPy (Oliphant 2006), Matplotlib (Hunter 2007), emcee (Foreman-Mackey et al. 2013), scikit-image (Van der Walt et al. 2014), scikit-learn (Pedregosa et al. 2012), photutils (Bradley et al. 2016), and astropy (Astropy Collaboration 2013, 2018) packages.
Funding AgencyGrant Number
European Research Council (ERC)678194
Deutsche Forschungsgemeinschaft (DFG)MU 2695/27-1
Fonds Wetenschappelijk Onderzoek (FWO)1280121N
Gaia Multilateral AgreementUNSPECIFIED
Ministerio de Economía, Industria y Competitividad (MINECO)AyA2017-84089
Subject Keywords:planets and satellites: detection / planets and satellites: formation / instrumentation: high angular resolution / techniques: image processing / stars: individual: TYC 8984-2245-1
Record Number:CaltechAUTHORS:20210423-164905025
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Official Citation:Discovery of a directly imaged planet to the young solar analog YSES 2 Alexander J. Bohn, Christian Ginski, Matthew A. Kenworthy, Eric E. Mamajek, Mark J. Pecaut, Markus Mugrauer, Nikolaus Vogt, Christian Adam, Tiffany Meshkat, Maddalena Reggiani and Frans Snik A&A, 648 (2021) A73 DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108847
Deposited By: George Porter
Deposited On:29 Apr 2021 19:42
Last Modified:29 Apr 2021 19:42

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