Forming Binary Near-Earth Asteroids From Tidal Disruptions

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ContentsList of TablesList of Figuresviiiix1 Introduction 11.1 Scientific Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1.1 Why binary asteroids are interesting . . . . . . . . . . . . . . . . 11.1.2 Binary near-Earth asteroids . . . . . . . . . . . . . . . . . . . . . 21.1.3 Binary Main-Belt asteroids . . . . . . . . . . . . . . . . . . . . . 61.2 Binary Formation Mechanisms . . . . . . . . . . . . . . . . . . . . . . . 91.2.1 Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121.2.2 Collisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121.2.3 Rotational disruption . . . . . . . . . . . . . . . . . . . . . . . . 141.3 Shape and Spin Distributions for NEAs and MBAs . . . . . . . . . . . . 171.3.1 Existing lightcurve data . . . . . . . . . . . . . . . . . . . . . . 171.3.2 Recent studies . . . . . . . . . . . . . . . . . . . . . . . . . . . 181.3.3 Motivation for work on small MBAs . . . . . . . . . . . . . . . . 191.4 Steady-State Models of the NEA Population . . . . . . . . . . . . . . . . 201.4.1 Near-Earth asteroid population dynamics . . . . . . . . . . . . . 211.5 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221.5.1 Tidal disruption . . . . . . . . . . . . . . . . . . . . . . . . . . . 221.5.2 Rubble piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241.6 This Dissertation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252 Formation of Binary Asteroids via Tidal Disruption of Rubble Piles 262.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262.2 Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272.2.1 Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272.2.2 Progenitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272.2.3 Tidal encounters and initial conditions . . . . . . . . . . . . . . 302.2.4 Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32v
2.3 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . 332.3.1 Bulk results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332.3.2 T-PROS and T-EEBs . . . . . . . . . . . . . . . . . . . . . . . . 452.3.3 Classes of disruption . . . . . . . . . . . . . . . . . . . . . . . . 472.3.4 3 h spin rate subset . . . . . . . . . . . . . . . . . . . . . . . . . 472.3.5 Triples and hierarchical systems . . . . . . . . . . . . . . . . . . 502.3.6 Tidal evolution and eccentricity damping . . . . . . . . . . . . . 502.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 553 Lightcurve Observations of Small Main Belt Asteroids 573.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 573.2 Observations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 583.3 Data Reduction and Photometry . . . . . . . . . . . . . . . . . . . . . . 603.3.1 Phase dispersion minimization . . . . . . . . . . . . . . . . . . . 613.4 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . 623.4.1 Well-determined lightcurves . . . . . . . . . . . . . . . . . . . . 633.4.2 Detections with significant constraints . . . . . . . . . . . . . . . 643.4.3 Marginal detections . . . . . . . . . . . . . . . . . . . . . . . . . 663.4.4 Spin and shape properties among small MBAs and NEAs . . . . . 743.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 784 Steady-State Model of the Binary Near-Earth Asteroid Population 804.0.1 Previous work . . . . . . . . . . . . . . . . . . . . . . . . . . . 814.1 Steady-State Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 834.1.1 Initial shape and spins . . . . . . . . . . . . . . . . . . . . . . . 834.1.2 NEA lifetimes and planetary encounters . . . . . . . . . . . . . . 844.1.3 Binary evolution . . . . . . . . . . . . . . . . . . . . . . . . . . 884.1.4 Migrating binary MBAs . . . . . . . . . . . . . . . . . . . . . . 924.2 Steady-State Results and Discussion . . . . . . . . . . . . . . . . . . . . 954.2.1 Nominal case . . . . . . . . . . . . . . . . . . . . . . . . . . . . 954.2.2 Influence of MBA binary percentage . . . . . . . . . . . . . . . . 964.2.3 Influence of MBA shape/spin properties . . . . . . . . . . . . . . 1014.2.4 Influence of tidal evolution . . . . . . . . . . . . . . . . . . . . . 1014.2.5 Estimates on the properties of binary NEAs formed by tidal disruption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1034.2.6 Estimates of migrated binaries’ numbers and properties . . . . . . 1044.2.7 Doublet craters . . . . . . . . . . . . . . . . . . . . . . . . . . . 1054.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1055 Conclusions 1085.1 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109vi
Page 1 and 2: AbstractTitle of Dissertation:Formi
Page 3 and 4: Forming Binary Near-Earth Asteroids
Page 5 and 6: PrefaceMuch of the work in this dis
Page 7: AcknowledgementsI would not have ma
Page 11 and 12: List of Tables1.1 Binary NEA proper
Page 13 and 14: 4.8 Percentage of migrated binaries
Page 15 and 16: of the system mass M by way of Kepl
Page 17 and 18: the largest lightcurve amplitudes o
Page 19 and 20: 1.1.3 Binary Main-Belt asteroidsRec
Page 21 and 22: Lightcurve discoveriesA lightcurve
Page 23 and 24: Figure 1.1: (Top) The primary rotat
Page 25 and 26: 1.2.1 CaptureIn this scenario two a
Page 27 and 28: ever, understanding the mechanism i
Page 29 and 30: off the equator or off one end of a
Page 31 and 32: 3 Denotes a secure result with no a
Page 33 and 34: nostic.Recent results have demonstr
Page 35 and 36: another intermediate source of NEAs
Page 37 and 38: 1.5.2 Rubble pilesThe evidence for
Page 39 and 40: Chapter 2Formation of Binary Astero
Page 41 and 42: ∼ 60%, making a bulk density of
Page 43 and 44: shedding mass and distorting prior
Page 45 and 46: Figure 2.3: Snapshots of a tidal di
Page 47 and 48: Figure 2.4: Normalized probability
Page 49 and 50: Figure 2.5: Normalized probability
Page 51 and 52: Figure 2.6: (a) Satellite eccentric
Page 53 and 54: various complications of measuring
Page 55 and 56: etween ω pri and L bin ), with clo
Page 57 and 58: prolate-like), the oblate-like bodi
Page 59 and 60:
Figure 2.9: Plots comparing T-PROS
Page 61 and 62:
Figure 2.10: Comparison of S-class
Page 63 and 64:
2.3.5 Triples and hierarchical syst
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a/R pri based on a simple conversio
Page 67 and 68:
Figure 2.13: The eccentricity dampi
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Main Belt. Work by Chauvineau & Far
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(1992), with a target range of slig
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The observations were made from the
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peaked period, with a lower signifi
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and suggests that it is possibly a
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fit for the period of the lightcurv
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Table 3.2.Orbital, physical and lig
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Figure 3.2: Asteroid lightcurves.70
Page 85 and 86:
Figure 3.4: Asteroid lightcurves.72
Page 87 and 88:
3.4.4 Spin and shape properties amo
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Figure 3.7: The lightcurve amplitud
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Typically observations of eclipse o
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Chapter 4Steady-State Model of the
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values between 0.2-0.6. There is on
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asteroids in the Main Belt is suffi
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Figure 4.2: Percent of surviving NE
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4.1.3 Binary evolutionBasic stabili
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Table 4.1.Lifetimes for binary NEAs
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which means it should have a critic
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Figure 4.4: The total number of bin
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the original eccentricity distribut
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Figure 4.6: Properties of the binar
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Figure 4.8: Binary percentage for m
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Figure 4.9: Effects of tidal evolut
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quickly altered, or involved in bin
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tidal disruption. However, the impl
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Chapter 5ConclusionsA general concl
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small additions to the angular mome
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cently this large pool of observers
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differences in results when a lower
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Table A.1.Number of binaries produc
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Thus the reaccumulated bodies in th
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of 2.2 h observed is significantly
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Benner, L. A. M., Nolan, M. C., Ost
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V7.0:LCREF TAB, 35, 4Harris, A. W.,
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Storrs, A. D., Close, L. M., & Mena
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122Pravec, P., Kušnirá, P., Hicks
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Shepard, M. K., Schlieder, J., Nola
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Forming Binary Near-Earth Asteroids From Tidal Disruptions

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