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DOI	10.1073/pnas.2017418118
	A backward-spinning star with two coplanar planets
	Hjorth M.; Albrecht S.; Hirano T.; Winn J.N.; Dawson R.I.; Zanazzi J.J.; Knudstrup E.; Sato B.
发表日期	2021
ISSN	00278424
卷号	118 期号:8
英文摘要	It is widely assumed that a star and its protoplanetary disk are initially aligned, with the stellar equator parallel to the disk plane. When observations reveal a misalignment between stellar rotation and the orbital motion of a planet, the usual interpretation is that the initial alignment was upset by gravitational perturbations that took place after planet formation. Most of the previously known misalignments involve isolated hot Jupiters, for which planet–planet scattering or secular effects from a wider-orbiting planet are the leading explanations. In theory, star/disk misalignments can result from turbulence during star formation or the gravitational torque of a wide-orbiting companion star, but no definite examples of this scenario are known. An ideal example would combine a coplanar system of multiple planets—ruling out planet–planet scattering or other disruptive postformation events—with a backward-rotating star, a condition that is easier to obtain from a primordial misalignment than from postformation perturbations. There are two previously known examples of a misaligned star in a coplanar multiplanet system, but in neither case has a suitable companion star been identified, nor is the stellar rotation known to be retrograde. Here, we show that the star K2-290 A is tilted by 124◦ ± 6◦ compared with the orbits of both of its known planets and has a wide-orbiting stellar companion that is capable of having tilted the protoplanetary disk. The system provides the clearest demonstration that stars and protoplanetary disks can become grossly misaligned due to the gravitational torque from a neighboring star. © 2021 National Academy of Sciences. All rights reserved.
英文关键词	Binary host; Exoplanets; Obliquity; Primordial inclination; System formation
语种	英语
scopus关键词	article; astronomy; orbit; rotation; theoretical study; torque
来源期刊	Proceedings of the National Academy of Sciences of the United States of America
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/180578
作者单位	Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Aarhus C, DK-8000, Denmark; Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo, 152-8551, Japan; Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, United States; Department of Astronomy and Astrophysics, Center for Exoplanets and Habitable Worlds, Pennsylvania State University, University Park, PA 16802, United States; Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON M5S 3H8, Canada
推荐引用方式 GB/T 7714	Hjorth M.,Albrecht S.,Hirano T.,et al. A backward-spinning star with two coplanar planets[J],2021,118(8).
APA	Hjorth M..,Albrecht S..,Hirano T..,Winn J.N..,Dawson R.I..,...&Sato B..(2021).A backward-spinning star with two coplanar planets.Proceedings of the National Academy of Sciences of the United States of America,118(8).
MLA	Hjorth M.,et al."A backward-spinning star with two coplanar planets".Proceedings of the National Academy of Sciences of the United States of America 118.8(2021).