Defining the Flora Family

Orbital properties, reflectance properties and age

Melissa J. Dykhuis, Lawrence Molnar, Samuel J. Van Kooten, Richard J. Greenberg

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

The Flora family resides in the densely populated inner main belt, bounded in semimajor axis by the ν6 secular resonance and the Jupiter 3:1 mean motion resonance. The presence of several large families that overlap dynamically with the Floras (e.g., the Vesta, Baptistina, and Nysa-Polana families), and the removal of a significant fraction of Floras via the nearby ν6 resonance complicates the Flora family's distinction in both proper orbital elements and reflectance properties. Here we use orbital information from the Asteroids Dynamic Site (AstDyS), color information from the Sloan Digital Sky Survey (SDSS), and albedo information from the Wide-field Infrared Survey Explorer (WISE) to obtain the median orbital and reflectance properties of the Floras by sampling the core of the family in multidimensional phase space. We find the median Flora SDSS colors to be a*=0.126±0.007 and i-z=-0.037±0.007; the median Flora albedo is pV=0.291±0.012. These properties allow us to define ranges for the Flora family in orbital and reflectance properties, as required for a detailed dynamical study. We use the young Karin family, for which we have an age determined via direct backward integration of members' orbits, to calibrate the Yarkovsky drift rates for the Flora family without having to estimate the Floras' material properties. The size-dependent dispersion of the Flora members in semimajor axis (the "V" plot) then yields an age for the family of 950-170+200My, with the uncertainty dominated by the uncertainty in the material properties of the family members (e.g., density and surface thermal properties). We discuss the effects on our age estimate of two independent processes that both introduce obliquity variations among the family members on short (My) timescales: (1) the capture of Flora members in spin-orbit resonance, and (2) YORP-driven obliquity variation through YORP cycles. Accounting for these effects does not significantly change this age determination.

Original languageEnglish (US)
Pages (from-to)111-128
Number of pages18
JournalIcarus
Volume243
DOIs
StatePublished - Nov 5 2014

Fingerprint

plants (botany)
reflectance
flora
orbitals
obliquity
albedo
family
Wide-field Infrared Survey Explorer
drift rate
orbits
color
orbital elements
chronology
estimates
age determination
asteroids
Jupiter (planet)
Jupiter
asteroid

Keywords

  • Asteroids
  • Asteroids, dynamics
  • Resonances, Spin-orbit

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Defining the Flora Family : Orbital properties, reflectance properties and age. / Dykhuis, Melissa J.; Molnar, Lawrence; Van Kooten, Samuel J.; Greenberg, Richard J.

In: Icarus, Vol. 243, 05.11.2014, p. 111-128.

Research output: Contribution to journalArticle

Dykhuis, Melissa J. ; Molnar, Lawrence ; Van Kooten, Samuel J. ; Greenberg, Richard J. / Defining the Flora Family : Orbital properties, reflectance properties and age. In: Icarus. 2014 ; Vol. 243. pp. 111-128.
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