Forming Binary Near-Earth Asteroids From Tidal Disruptions

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Comparison with binary NEAsThe application of lightcurve techniques to small MBAs may define the role that asteroidsize plays in binary fractions and properties. These recent discoveries suggest thepreviously perceived differences between NEA and MBA binaries may have been dominatedby the relative difference in size of observed bodies as well as the fundamentalobserving biases affecting each. If the small MBA binaries have very similar propertiesto NEAs, then a similar formation mechanism will be needed for both MBAs and NEAs,and potential transport of MBAs to the NEA population will be important. These newlydiscovered binary small MBAs with rapidly rotating primaries, small size-ratios and smallseparations suggest that the formation mechanism for binary NEAs may also be creatingbinaries of a similar sort in the Main Belt.1.2 <strong>Binary</strong> Formation MechanismsUntil very recently different formation mechanisms were typically invoked to explain binaryNEAs and MBAs: rotational spin-up and collisional processes respectively. <strong>Tidal</strong>disruption, as a means of rotational disruption, fit the binary NEAs, as encounters withlarge planetary bodies are unique to that region and frequent enough to affect a largepercentage of the population. In the Main Belt collisional lifetimes are shorter than dynamicallifetimes, providing a framework for the formation of the diverse population ofbinary MBAs. The recent work on small binary MBAs calls into question these separateformation mechanisms and may demand a new formation mechanism which will affectsmall bodies in both populations. Below we discuss the main binary formation mechanismsexpected to be acting throughout the inner Solar System.9
Figure 1.1: (Top) The primary rotation period of the known NEA (filled) and MBA(open) binaries as a function of the pericenter of the binary’s orbit. (Bottom) The componentseparations of the same binaries as a function of pericenter. In both panels, eachpoint represents one binary, with the size of the point indicating the size of the primary.10
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 and 8: AcknowledgementsI would not have ma
Page 9 and 10: 2.3 Results and Discussion . . . .
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: Lightcurve discoveriesA lightcurve
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
Page 65 and 66: a/R pri based on a simple conversio
Page 67 and 68: Figure 2.13: The eccentricity dampi
Page 69 and 70: Main Belt. Work by Chauvineau & Far
Page 71 and 72: (1992), with a target range of slig
Page 73 and 74:
The observations were made from the
Page 75 and 76:
peaked period, with a lower signifi
Page 77 and 78:
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
Page 93 and 94:
Chapter 4Steady-State Model of the
Page 95 and 96:
values between 0.2-0.6. There is on
Page 97 and 98:
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
Page 107 and 108:
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
Page 113 and 114:
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
Page 121 and 122:
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
Page 131 and 132:
Thus the reaccumulated bodies in th
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of 2.2 h observed is significantly
Page 135 and 136:
Benner, L. A. M., Nolan, M. C., Ost
Page 137 and 138:
V7.0:LCREF TAB, 35, 4Harris, A. W.,
Page 139 and 140:
Storrs, A. D., Close, L. M., & Mena
Page 141 and 142:
122Pravec, P., Kušnirá, P., Hicks
Page 143 and 144:
Shepard, M. K., Schlieder, J., Nola
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Forming Binary Near-Earth Asteroids From Tidal Disruptions

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