The McDonald Accelerating Stars Survey: Architecture of the Ancient Five-Planet Host System Kepler-444

Zhoujian Zhang*, Brendan P. Bowler, Trent J. Dupuy, Timothy D. Brandt, G. Mirek Brandt, William D. Cochran, Michael Endl, Phillip J. MacQueen, Kaitlin M. Kratter, Howard T. Isaacson, Kyle Franson, Adam L. Kraus, Caroline V. Morley, Yifan Zhou

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

We present the latest and most precise characterization of the architecture for the ancient (≈11 Gyr) Kepler-444 system, which is composed of a K0 primary star (Kepler-444 A) hosting five transiting planets and a tight M-type
spectroscopic binary (Kepler-444 BC) with an A–BC projected separation of 66 au. We have measured the system’s relative astrometry using the adaptive optics imaging from Keck/NIRC2 and Kepler-444 A’s radial velocities from the Hobby-Eberly Telescope and reanalyzed relative radial velocities between BC and A from
Keck/HIRES. We also include the Hipparcos-Gaia astrometric acceleration and all published astrometry and radial velocities in an updated orbit analysis of BC’s barycenter. These data greatly extend the time baseline of the monitoring and lead to significant updates to BC’s barycentric orbit compared to previous work, including a larger semimajor axis (a 52.2 2.73.3= -+ au), a smaller eccentricity (e = 0.55 ± 0.05), and a more precise inclination (i=85 . 4+0 .3-0.1). We have also derived the first dynamical masses of B and C components. Our results suggest that Kepler-444 A’s protoplanetary disk was likely truncated by BC to a radius of ≈8 au, which resolves the previously noticed tension between Kepler-444 A’s disk mass and planet masses. Kepler-444 BC’s barycentric orbit is likely aligned with those of A’s five planets, which might be primordial or a consequence of dynamical evolution. The Kepler-444 system demonstrates that compact multiplanet systems residing in hierarchical stellar triples can form
at early epochs of the universe and survive their secular evolution throughout cosmic time.
Original languageEnglish
Article number73
Pages (from-to)1-18
Number of pages18
JournalAstronomical Journal
Issue number2
Publication statusPublished - 27 Jan 2023

Keywords / Materials (for Non-textual outputs)

  • Spin-Orbit alignment
  • Gravitational Instabilities
  • Planetary system
  • Binary-systems
  • Mass
  • Companion:I
  • Multiplicity; II
  • Perturbations


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