arXiv · 2410.00213
The Compositions of Rocky Planets in Close-in Orbits Tend to be Earth-Like
Abstract
Hundreds of exoplanets between 1-1.8 times the size of the Earth have been discovered on close in orbits. However, these planets show such a diversity in densities that some appear to be made entirely of iron, while others appear to host gaseous envelopes. To test this diversity in composition, we update the masses of 5 rocky exoplanets (HD 93963 A b, Kepler-10 b, Kepler-100 b, Kepler-407 b, and TOI-1444 b) and present the confirmation of a new planet (TOI-1011) using 187 high precision RVs from Gemini/MAROON-X and Keck/KPF. Our updated planet masses suggest compositions closer to that of the Earth than previous literature values for all planets in our sample. In particular, we report that two previously identified ``super-Mercuries'' (Kepler-100 b and HD 93963 A b) have lower masses that suggest less iron-rich compositions. We then compare the ratio of iron to rock-building species to the abundance ratios of those elements in their host stars. These updated planet compositions do not suggest a steep relationship between planet and host star compositions, contradictory to previous results, and suggest that planets and host stars have similar abundance ratios.
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Casey L. Brinkman, Lauren M. Weiss, Daniel Huber, Rena A. Lee, Jared Kolecki, Gwyneth Tenn, Jingwen Zhang, Suchitra Narayanan, Alex S. Polanski, Fei Dai, Jacob L. Bean, Corey Beard, Madison Brady, Max Brodheim, Matt Brown, William Deich, Jerry Edelstein, Benjamin J. Fulton, Steven Giacalone, Steven R. Gibson, Gregory J. Gilbert, Samuel Halverson, Luke Handley, Grant M. Hill, Rae Holcomb, Bradford Holden, Aaron Householder, Andrew W. Howard, Howard Isaacson, Stephen Kaye, Russ R. Laher, Kyle Lanclos, J. M. Joel Ong, Joel Payne, Eric A. Petigura, Daria Pidhorodetska, Claire Poppett, Arpita Roy, Ryan Rubenzahl, Nicholas Saunders, Christian Schwab, Andreas Seifahrt, Abby P. Shaum, Martin M. Sirk, Chris Smith, Roger Smith, Guðmundur Stefánsson, Julian Stürmer, Jim Thorne, Emma V. Turtelboom, Dakotah Tyler, John Valliant, Judah Van Zandt, Josh Walawender, Samuel W. Yee, Sherry Yeh, Jon Zink. 2024-09-30. The Compositions of Rocky Planets in Close-in Orbits Tend to be Earth-Like. https://arxiv.org/abs/2410.00213
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