该研究团队利用径向速度观测技术，发现了一颗海王星质量的系外行星，它围绕着LHS 3154运行，其是一颗质量比太阳小9倍的恒星。该系外行星的轨道周期较短，仅为3.7天，并且其最小质量也是地球质量的13.2倍。研究人员通过模拟实验发现，这种高行星-恒星质量比(大于3.5 × 10-3)并不是核心吸积理论或行星形成引力不稳定性理论的预期结果。
在核心吸积模拟实验中，研究人员发现，只有在原行星盘的尘埃质量比通常在低质量恒星周围观察到的大一个数量级的情况下，才可能形成海王星大小的近距离行星。
据悉，行星形成理论预测，质量较小的恒星很少拥有质量超过海王星的系外行星。
附：英文原文
Title: A Neptune-mass exoplanet in close orbit around a very low-mass star challenges formation models
Author: Guoemundur Stefánsson, Suvrath Mahadevan, Yamila Miguel, Paul Robertson, Megan Delamer, Shubham Kanodia, Caleb I. Caas, Joshua N. Winn, Joe P. Ninan, Ryan C. Terrien, Rae Holcomb, Eric B. Ford, Brianna Zawadzki, Brendan P. Bowler, Chad F. Bender, William D. Cochran, Scott Diddams, Michael Endl, Connor Fredrick, Samuel Halverson, Fred Hearty, Gary J. Hill, Andrea S. J. Lin, Andrew J. Metcalf, Andrew Monson, Lawrence Ramsey, Arpita Roy, Christian Schwab, Jason T. Wright, Gregory Zeimann
Issue&Volume: 2023-12-01
Abstract: Theories of planet formation predict that low-mass stars should rarely host exoplanets with masses exceeding that of Neptune. We used radial velocity observations to detect a Neptune-mass exoplanet orbiting LHS 3154, a star that is nine times less massive than the Sun. The exoplanet’s orbital period is 3.7 days, and its minimum mass is 13.2 Earth masses. We used simulations to show that the high planet-to-star mass ratio (>3.5 × 10-3) is not an expected outcome of either the core accretion or gravitational instability theories of planet formation. In the core-accretion simulations, we show that close-in Neptune-mass planets are only formed if the dust mass of the protoplanetary disk is an order of magnitude greater than typically observed around very low-mass stars.
DOI: 10.1126/science.abo0233
Source: https://www.science.org/doi/10.1126/science.abo0233