A quantitative criterion for defining planets
Open accessAbstract
A simple metric can be used to determine whether a planet or exoplanet can clear its orbital zone during a characteristic time scale, such as the lifetime of the host star on the main sequence. This criterion requires only estimates of star mass, planet mass, and orbital period, making it possible to immediately classify 99% of all known exoplanets. All eight planets and all classifiable exoplanets satisfy the criterion. This metric may be useful in generalizing and simplifying the definition of a planet.
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A lower limit on the mass arises from the IAU definition of a planet: the body must be massive enough to clear its orbit over the age of the solar system, implying that the minimum planetary mass is an increasing function of orbital distance.
“A lower limit on the mass arises from the definition of a planet. One of the characteristics of planets specified by the International Astronomical Union is that the body must be massive enough to clear its orbit over the age of the solar system. This requirement can be written in several di erent forms, and implies that the minimum planetary mass is an increasing function of orbital distance.”
From The planet nine hypothesis (2019) · cites this paper as Margot (2015)
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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
“Here we use the constraint advocated by Margot (2015), which can be written in the form Π = k m M a9/8 > 1 or m >∼ 1 M⊕ ( a 380AU )9/8 .”
Method
- Authors
- Margot, J.-L.
- Affiliations
- University of California, Los Angeles (US)
- Corresponding author
- Margot, Jean-Luc
- ORCID
- Margot, Jean-Luc
- Venue
- The Astronomical Journal
- Publisher
- American Astronomical Society
- Published
- 2015-12-01
- Volume
- 150
- Issue
- 6
- Pages
- 185
- ISSN
- 0004-6256 (ISSN-L)
- 1538-3881
- OpenAlex
- W2106500959
- Cited by
- 21
- References
- 0
- Citations by year
- 2026: 2 · 2025: 2 · 2024: 3 · 2023: 1 · 2022: 5 · 2021: 2 · 2020: 2 · 2019: 1 · 2018: 2 · 2017: 1
- FWCI
- 0.57
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Licence
- Locations
- The Astronomical Journal (publishedVersion)
- arXiv (Cornell University) (submittedVersion)
- Funders
- National Aeronautics and Space Administration
- California Institute of Technology
- 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
- planet definition, exoplanets, planetary mass, orbital period, main-sequence lifetime
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