THE MASS-RADIUS RELATION FOR 65 EXOPLANETS SMALLER THAN 4 EARTH RADII
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We study the masses and radii of 65 exoplanets smaller than 4 R ⊕ with orbital periods shorter than 100 days. We calculate the weighted mean densities of planets in bins of 0.5 R ⊕ and identify a density maximum of 7.6 g cm −3 at 1.4 R ⊕ . On average, planets with radii up to R P = 1.5 R ⊕ increase in density with increasing radius. Above 1.5 R ⊕ , the average planet density rapidly decreases with increasing radius, indicating that these planets have a large fraction of volatiles by volume overlying a rocky core. Including the solar system terrestrial planets with the exoplanets below 1.5 R ⊕ , we find ρ P = 2.43 + 3.39( R P / R ⊕ ) g cm −3 for R P < 1.5 R ⊕ , which is consistent with rocky compositions. For 1.5 ⩽ R P / R ⊕ < 4, we find M P / M ⊕ = 2.69( R P / R ⊕ ) 0.93 . The rms of planet masses to the fit between 1.5 and 4 R ⊕ is 4.3 M ⊕ with reduced χ 2 = 6.2. The large scatter indicates a diversity in planet composition at a given radius. The compositional diversity can be due to planets of a given volume (as determined by their large H/He envelopes) containing rocky cores of different masses or compositions.
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For a mass range between 5 and 10 M, exoplanets follow an approximate power law R ∝ (M/M)^0.55, suggesting radii of 2.4 and 3.5 R, respectively.
“For a mass range between 5 and 10 M , exoplanets follow an approximate power law where R R ( M = M ) 0 : 55 , suggesting radii of 2 : 4 and 3 : 5 R , respectively (Weiss and Marcy, 2014).”
From The planet nine hypothesis (2019) · cites this paper as Weiss and Marcy, 2014
Analyses of mass-radius relationships suggest a break point around 1.7 Earth radii (~5 Earth masses); above that size, increasingly larger planets have a composition increasingly dominated by H2/He gas.
“The analyses of these relationships suggest a “break point” around 1.7 Earth radii (∼5 Earth masses); above that size, increasingly larger planets have a composition that is increasingly dominated by H2/He gas.”
From The Astrobiology Primer v2.0 (2016) · cites this paper as Weiss and Marcy, 2014
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A super-Earth transiting a nearby low-mass star
Charbonneau, D., Berta, Z. K., Irwin, J., Burke, C. J., Nutzman, P., Buchhave, L. A., Lovis, C., Bonfils, X., Latham, D. W., Udry, S., et al. (2009) · Nature · doi:10.1038/nature08679 · Cited by 797 · see citing works
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Batygin, K., Adams, F. C., Brown, M. E., & Becker, J. C. (2019) · Physics Reports · doi:10.1016/j.physrep.2019.01.009 · Cited by 181 · see citing works
“5R⊕, respectively (Weiss and Marcy, 2014).”
Domagal-Goldman, S. D., Wright, K. E., Domagal-Goldman, S. D., Wright, K. E., Adamala, K., Arina de la Rubia, L., Bond, J., Dartnell, L. R., Goldman, A. D., Lynch, K., et al. (2016) · Astrobiology · doi:10.1089/ast.2015.1460 · Cited by 136 · see citing works
“This has allowed the first attempts at creating mass-radius relationships for extrasolar planets (e.g., Wolfgang and Laughlin, 2011; Lopez and Fortney, 2013; Weiss and Marcy, 2014).”
- Authors
- Weiss, L. M., & Marcy, G. W.
- Affiliations
- University of California, Berkeley (US)
- ORCID
- Weiss, Lauren M.
- Venue
- The Astrophysical Journal
- Publisher
- American Astronomical Society
- Published
- 2014-02-13
- Volume
- 783
- Issue
- 1
- Pages
- L6
- ISSN
- 2041-8205 (ISSN-L)
- 2041-8213
- OpenAlex
- W1967414563
- Cited by
- 665
- References
- 1
- Citations by year
- 2026: 13 · 2025: 25 · 2024: 41 · 2023: 34 · 2022: 30 · 2021: 39 · 2020: 58 · 2019: 67 · 2018: 114 · 2017: 81 · 2016: 72 · 2015: 54 · 2014: 35
- FWCI
- 43.48
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Licence
- Locations
- The Astrophysical Journal Letters (publishedVersion)
- arXiv (Cornell University) (submittedVersion)
- arXiv (Cornell University)
- Topics
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Stellar, planetary, and galactic studies
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astro and Planetary Science
- Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Space Science and Extraterrestrial Life
- Keywords
- mass-radius relation, exoplanets, super-Earths, planet density, planetary composition, rocky core, terrestrial planets, compositional diversity, hot Jupiters
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