リング模様が示す、まだ見ぬ惑星と塵が自ら集まる仕組み ー太陽系の外側にあたる遠い場所でも惑星の材料が集まることを示唆ー

2026-10-15 九州大学

V1094 Scoの円盤の想像図（イラスト：大学院理学府 地球惑星科学専攻 博士課程2年 Yurika Nakamura）

＜関連情報＞

• https://www.kyushu-u.ac.jp/ja/researches/view/1597
• https://iopscience.iop.org/article/10.3847/1538-4357/ae819b

巨大原始惑星系円盤V1094 Scoにおける複数のリングギャップ構造のハイブリッド起源：低質量惑星と永年重力不安定性 A Hybrid Origin for the Multiple Ring-gap Structures in the Large Protoplanetary Disk V1094 Sco: A Low-mass Planet and Secular Gravitational Instability

Masayuki Yamaguchi, Masahiro N. Machida, Ryosuke T. Tominaga, Jinshi Sai, Takayuki Muto, Michihiro Takami, Hauyu Baobab Liu, Ayumu Shoshi, Takashi Tsukagoshi, and Shu Ishibashi
The Astrophysical Journal  Published: 2026 July 29
DOI:10.3847/1538-4357/ae819b

Abstract

High spatial resolution observations reveal that some protoplanetary disks host multiple ring–gap pairs at large stellocentric radii, yet their physical origin remains unsettled. We present a multiwavelength analysis of the V1094 Sco disk using Atacama Large Millimeter/submillimeter Array Band 6 continuum and ¹²CO and ¹³CO J = 2–1 emission, together with a Very Large Telescope/SPHERE near-infrared scattered-light image. The continuum image shows four narrow dust ring–gap pairs extending to exceptionally large radii (r ∼ 380 au), while the CO isotopologues trace a spatially extended gas disk (r ∼ 760 au) in Keplerian rotation. From the dust ring widths, we place conservative upper limits on the turbulent viscosity parameter, α ≲ 10⁻³ and potentially ≲10⁻⁴, implying weak turbulence. The ensemble of gap widths and depths is inconsistent with a simple one-planet-per-gap interpretation. At r ≃ 100 au, a double gap and its scattered-light counterpart are consistent with multigap excitation by a single low-mass companion of (55 ± 35) M_⊕. At r ≃ 170–230 au, the outer ring system shows regular spacing and no clear scattered-light counterpart, indicating mechanisms that operate primarily at the disk midplane. These outer rings are quantitatively compatible with secular gravitational instability. V1094 Sco therefore supports a hybrid pathway in which weak turbulence in an extended disk allows secular gravitational instability to assemble long-lived midplane dust concentrations that can cradle planet formation beyond ∼100 au, alongside planet-driven substructures at intermediate radii.