OSSOS XX: The Meaning of Kuiper Belt Colors

David Nesvorný, David Vokrouhlický, Mike Alexandersen, Michele T. Bannister, Laura E. Buchanan, Ying Tung Chen, Brett J. Gladman, Stephen D.J. Gwyn, J. J. Kavelaars, Jean Marc Petit, Megan E. Schwamb, Kathryn Volk

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Abstract

Observations show that 100 km class Kuiper Belt objects (KBOs) can be divided into (at least) two color groups, red (R; g-i < 1.2) and very red (VR; g-i > 1.2), reflecting a difference in their surface composition. This is thought to imply that KBOs formed over a relatively wide range of radial distance, r. The cold classicals at 42 au < r < 47 au are predominantly VR, and known Neptune Trojans at r ≃ 30 au are mostly R. Intriguingly, however, the dynamically hot KBOs show a mix of R and VR colors and no correlation of color with r. Here we perform migration/instability simulations where the Kuiper Belt is populated from an extended planetesimal disk. We find that the color observations can be best understood if R objects formed at r < r∗ and VR objects at r > r∗, with 30 au < r∗ < 40 au. The proposed transition at 30 au < r∗ < 40 au would explain why the VR objects in the dynamically hot population have smaller orbital inclinations than the R objects, because the orbital excitation from Neptune weakens for orbits starting beyond 30 au. Possible causes of the R-VR color bimodality are discussed.

Original languageEnglish
Article number46
JournalAstronomical Journal
Volume160
Issue number1
DOIs
Publication statusPublished - 29 Jun 2020

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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