Forming Binary Near-Earth Asteroids From Tidal Disruptions

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Figure 2.8: (a) Ratio of axes a/c for primaries of resultant binary systems. (b) Ratio ofaxes a/b. (c) Ratio of axes a/b separated into prolate (thin lines) and oblate (thick lines,cross hatch fill). (d) Ratio of I =(a-b)/(a-c), showing whether the intermediate axis b iscloser to a, making the body oblate-like, or closer to c, making the body prolate-like.43
prolate-like), the oblate-like bodies account for nearly half of these that have a/b < 1.2;few oblate-like bodies have a/b > 1.5 (Fig. 2.8c).As mentioned above, virtually no bodies were perfectly oblate or prolate. The value Iwas computed for all primaries, which describes how near the body was to being exactlyprolate or oblate (Fig. 2.8d). The plot shows that many bodies are very nearly completelyprolate with b nearly equal to c. Conversely oblate-like primaries are frequently onlymildly oblate, with b nearly evenly between a and c.The observed population of NEA binaries typically have quite spherical primaries,where in most cases amplitude of the lightcurve is used to interpret the shape of the body.Some elongations could potentially be larger if the lightcurve amplitudes are artificiallylow due to non-ideal viewing angles. The simulations produce some low-elongation primaries,but relatively few in comparison with high-elongation bodies with elongationabove 2.0. Furthermore, the simulated low-elongation primaries have a high probabilityof appearing oblate. When isolated, the low-elongation primaries show no properties suggestingthat they are more likely to have small separation or other properties related to theobserved binary population. They have a slight trend toward lower eccentricity, possiblysuggesting that the lack of observed high elongation primaries may be more related to survival,as opposed to formation. For example, how many of the currently observed binariescould survive with a primary of elongation 1.5 or 2.0? With all observed binaries havingsimilarly small separations, studying orbital stability around irregularly shaped primariesis appropriate. An answer may be found in large-separation NEA binaries (when/if theyare discovered), where elongated primaries would have a less significant impact on thedynamics of the binary orbit, so the binaries may have a better chance of surviving longenough to be observed.44
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 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: etween ω pri and L bin ), with clo
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
Page 79 and 80: fit for the period of the lightcurv
Page 81 and 82: Table 3.2.Orbital, physical and lig
Page 83 and 84: 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
Page 89 and 90: Figure 3.7: The lightcurve amplitud
Page 91 and 92: 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
Page 99 and 100: Figure 4.2: Percent of surviving NE
Page 101 and 102: 4.1.3 Binary evolutionBasic stabili
Page 103 and 104: Table 4.1.Lifetimes for binary NEAs
Page 105 and 106: 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
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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
Page 135 and 136:
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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