2025-08-06 カリフォルニア大学サンタバーバラ校（UCSB）
Photo Credit:Lauren Biddle, The University of Texas at Austin
About a third of the 49 young isolated stars surveyed by the researchers were found to be misaligned with their protoplanetary disk.
＜関連情報＞
- https://news.ucsb.edu/2025/021984/some-young-suns-are-aligned-their-planet-forming-disks-others-are-born-tilted
- https://www.nature.com/articles/s41586-025-09324-0
太陽類似星の3分の1は、惑星形成円盤が不揃いな状態で誕生する One-third of Sun-like stars are born with misaligned planet-forming disks
Lauren I. Biddle,Brendan P. Bowler,Marvin Morgan,Quang H. Tran & Ya-Lin Wu
Nature Published:06 August 2025
DOI:https://doi.org/10.1038/s41586-025-09324-0
Abstract
Exoplanets are organized in a broad array of orbital configurations1,2 that reflect their formation along with billions of years of dynamical processing through gravitational interactions3. This history is encoded in the angular momentum architecture of planetary systems—the relation between the rotational properties of the central star and the orbital geometry of planets. A primary observable is the alignment (or misalignment) between the rotational axis of the star and the orbital plane of its planets, known as stellar obliquity. Hundreds of spin–orbit constraints have been measured for giant planets close to their host stars4, many of which have revealed planets on misaligned orbits. A leading question that has emerged is whether stellar obliquity originates primarily from gravitational interactions with other planets or distant stars in the same system, or if it is ‘primordial’—imprinted during the star-formation process. Here we present a comprehensive assessment of primordial obliquities between the spin axes of young, isolated Sun-like stars and the orientation of the outer regions of their protoplanetary disks. Most systems are consistent with angular momentum alignment but about one-third of isolated young systems exhibit primordial misalignment. This suggests that some obliquities identified in planetary systems at older ages—including the Sun’s modest misalignment with planets in the Solar System—could originate from initial conditions of their formation.
