Planetesimals To Brown Dwarfs: What is a Planet?

Abstract

The past 15 years have brought about a revolution in our understanding of our Solar System and other planetary systems. During this time, discoveries include the first Kuiper Belt Objects, the first brown dwarfs, and the first extra-solar planets. Although discoveries continue apace, they have called into question our previous perspectives on planets, both here and elsewhere. The result has been a debate about the meaning of the word ''planet'' itself. It became clear that scientists do not have a widely accepted or clear definition of what a planet is, and both scientists and the public are confused (and sometimes annoyed) by its use in various contexts. Because ''planet'' is a very widely used term, it seems worth the attempt to resolve this problem. In this essay, we try to cover all the issues that have come to the fore, and bring clarity (if not resolution) to the debate.

23 pages

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• The SOPHIE search for northern extrasolar planets. IV. Massive companions in the planet-brown dwarf boundary
• What is a planet?
• The Dawes Review 3: The Atmospheres of Extrasolar Planets and Brown Dwarfs
• Production of trans-Neptunian binaries through chaos-assisted capture
• Considerations for Atmospheric Retrieval of High-Precision Brown Dwarf Spectra
• The IAU Working Definition of an Exoplanet
• Moons Are Planets: Scientific Usefulness Versus Cultural Teleology in the Taxonomy of Planetary Science
• The Albedos, Sizes, Colors and Satellites of Dwarf Planets Compared with Newly Measured Dwarf Planet 2013 FY27
• Simultaneous compression and opacity data from time-series radiography with a Lagrangian marker
• Early evidence for isotropic planetary obliquities in young super-Jupiter systems