A Neptune-mass exoplanet in close orbit around a very low-mass star challenges formation models

Guòmundur Stefánsson, Suvrath Mahadevan, Yamila Miguel, Paul Robertson, Megan Delamer, Shubham Kanodia, Caleb I. Cañas, 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 HalversonFred Hearty, Gary J. Hill, Andrea S.J. Lin, Andrew J. Metcalf, Andrew Monson, Lawrence Ramsey, Arpita Roy, Christian Schwab, Jason T. Wright, Gregory Zeimann

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


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 × 10-4) 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.

Original languageEnglish (US)
Pages (from-to)1031-1035
Number of pages5
Issue number6674
StatePublished - Dec 1 2023

All Science Journal Classification (ASJC) codes

  • General

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