2026-09-29 カリフォルニア大学リバーサイド校（UCR）
The binary star system 70 Ophiuchi AB, or 70 Oph AB, can be seen near the center of this image taken by the U.S. Naval Observatory in 1937.
＜関連情報＞
- https://news.ucr.edu/articles/2026/09/29/earth-planet-two-suns
- https://iopscience.iop.org/article/10.3847/1538-4357/ae9f52
70 Oph ABの視線速度および位置天文学的観測の1世紀：新たなPFSデータと惑星伴星の可能性に関する制約 A Century of Radial-velocity and Astrometric Monitoring of 70 Oph AB: New PFS Data and Constraints on Possible Planetary Companions
Yiting Li, Michael R. Meyer, Skylar D’Angiolillo, Stephen R. Kane, R. Paul Butler, Stephen A. Shectman, Eric E. Mamajek, Johanna Teske, Jack Lubin, Paul Robertson,…
The Astrophysical Journal Published: 2026 September 29
DOI:10.3847/1538-4357/ae9f52
Abstract
At a distance of 5.1 pc, the 70 Oph AB binary star system is one of the most favorable targets for future direct imaging and astrometry missions surveying mature, terrestrial planets. We present new radial velocities (RVs) obtained with the Planet Finder Spectrograph (PFS) on the 6.5 m Magellan II Clay Telescope in Chile. We collected 499 measurements of 70 Oph A and 334 measurements of 70 Oph B during 2023–2025. Combining these data with decades of archival RVs and astrometry, we derive an updated orbital solution for the binary and dynamical masses of 0.88 ± 0.004 and 0.73 ± 0.003 M⊙ for the primary and secondary components, respectively. We find that the long-term RV variability of both components is consistent with stellar activity modulated by rotation periods, and we detect no coherent planetary signals in either component. We place upper limits on any planets orbit in the plane of the binary. The 27 yr RV baseline for 70 Oph A excludes Jupiter-mass planets interior to 5 au and reaches sensitivity of 0.3 MJup at 1 au or 0.5 MJup at 2 au. For 70 Oph B, with PFS data we rule out planets more massive than 0.25–0.3 MJup inside 0.5 au. We show that stable S-type orbits around 70 Oph A extend to ∼2.5 au, covering the habitable zone. Thus, Saturn-mass planets or smaller on stable orbits in the habitable zone of 70 Oph A are allowed. Overall, our results provide important guidance for future planet searches around this stellar system.
