Photometric survey of binary near-Earth asteroids

Pravec, Petr; Scheirich, P.; Kušnirák, P.; Šarounová, L.; Mottola, S.; Hahn, Gerhard; Brown, Peter; Esquerdo, G.; Kaiser, N.; Krzeminski, Z.

doi:10.1016/j.icarus.2005.10.014

Cited by 294 publications

(339 citation statements)

References 41 publications

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“…A population of asynchronous binary asteroids among main belt asteroids (MBAs) smaller than 10 km was found recently (see Pravec et al 2006, and references therein; examples of recently detected ones see, e.g., Warner et al 2005Warner et al , 2006Pray et al 2006a, b;Higgins et al 2006a, b;Jakubík et al 2005;Cooney et al 2006). The asynchronous MBA binaries are similar to the NEA binaries in most characteristics.…”

Section: Binariesmentioning

confidence: 86%

“…Twenty of them were resolved with radar observations (see Ostro et al, 2006), and 15 were resolved with the photometric technique (see Pravec et al, 2006; and two new ones by Reddy et al, 2005Reddy et al, , 2006a; five were detected by both techniques.…”

Section: Binariesmentioning

confidence: 99%

“…In addition to the asynchronous binaries population among NEAs as well as small MBAs, there is also a smaller population of fully synchronous, nearly equal sized binaries (D s /D p nearly 1). Such systems appear to be infrequent among NEAs, with only one such system having been found so far, 69230 Hermes (Margot et al 2006; see also Pravec et al 2006, and reference therein). Among small MBAs, a few such systems with sizes around 10 km have been found by Behrend et al (2006) and Kryszczynska et al (2005).…”

Section: Binariesmentioning

confidence: 99%

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NEA rotations and binaries

2006

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Abstract. Of the nearly 3900 near-Earth asteroids (NEAs) known as of June 2006, 325 have estimated rotation periods, with most of those determined by lightcurve analysis led by a few dedicated programs. NEAs with diameters down to 10 meters have been sampled. Observed spin distribution shows a major changing point around diameter of 200 meters. Larger NEAs show a barrier against spins faster than 11 d −1 (period about 2.2 h) that shifts to slower rates (longer periods) with increasing lightcurve amplitude (i.e., with increasing equatorial elongation). The spin barrier is interpreted as a critical spin rate for bodies in a gravity regime; NEAs larger than 200 meters are predominantly bodies with tensile strength too low to withstand a centrifugal acceleration for rotation faster than the critical spin rate. The cohesionless spin barrier disappears at sizes less than 200 meters where most objects rotate too fast to be held together by self-gravitation only, so a cohesion is implied in the smaller NEAs.The distribution of NEA spin rates in the cohesionless size range (D > 0.2 km) is highly nonMaxwellian, suggesting that mechanisms other than just collisions have been at work. There is a pile up just in front of the barrier, at periods 2-3 h. It may be related to a spin up mechanism crowding asteroids to the barrier. An excess of slow rotators is observed at periods longer than 30 hours. A spin-down mechanism has no obvious lower limit on spin rate; periods as long as tens of days have been observed.Most NEAs appear to be in their basic spin states with rotation around principal axis with maximum moment of inertia. Tumbling objects (i.e., bodies in excited, non-principal axis rotation) are present and actually predominate among slow rotators with estimated damping timescales longer than the age of the solar system. A few tumblers observed among fast rotating coherent objects appear to be either more rigid or younger than the larger (cohesionless) tumblers.An abundant population of binary systems has been found among NEAs. The fraction of binaries among NEAs larger than 0.3 km has been estimated to be 15 ± 4%. Primaries of binary systems concentrate at fast spin rates (periods 2-3 h) and low amplitudes, i.e., they lie just below the cohesionless spin barrier. The total angular momentum content in binary systems suggests that they formed from parent bodies spinning at the critical rate. The fact that a very similar population of binaries has been found among small main belt asteroids suggests a binary formation mechanism that may not be related to close encounters with the terrestrial planets.

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Section: Binariesmentioning

confidence: 86%

Section: Binariesmentioning

confidence: 99%

Section: Binariesmentioning

confidence: 99%

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NEA rotations and binaries

2006

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“…(3) Diameter value estimated from direct albedo measurements by excess thermal emission in Reddy et al (2006). (4) Albedo estimated from radar diameter measurements (0.75 km) in Pravec et al (2006).…”

Section: Notesmentioning

confidence: 99%

Observations, compositional, and physical characterization of near-Earth and Mars-crosser asteroids from a spectroscopic survey

León

Licandro

Serra-Ricart

et al. 2010

A&A

106

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Aims. We analyse a significantly large sample of spectroscopic data to provide a compositional characterization of the near-Earth asteroid population. We present visible and near-infrared spectra of a total of 74 near-Earth asteroids (NEAs) and Mars-crossers (MCs), covering the wavelength region from 0.5 to 2.5 μm. Using spectra of NEAs from other databases to enlarge our sample, and compiling two comparison samples of main belt asteroids (MBs) and ordinary chondrites (OCs), we analyse a total of 79 NEAs, 91 MBs, and 103 OCs. Methods. We obtained our visible and near-infrared spectra using the instruments and the telescopes located at "El Roque de los Muchachos" Observatory, in the island of La Palma (Spain). We compute several diagnostic spectral parameters from the reflectance spectra of NEAs, MBs, and OCs, that are used to infer the mineralogical composition. The distribution of the obtained values are analysed in 2 different parameter spaces. We also apply a robust statistical method based on neuronal networks to those spectral parameters, to compare the NEAs with OCs. Space weathering effects and dynamical and physical properties of NEAs and MBs are also studied. Results. Compositional differences between MBs and NEAs are inferred from the mineralogical analysis. The most remarkable results are: (1) the high olivine content of the NEAs; (2) the compositional similarity between NEAs and a small group of meteorites, the LL ordinary chondrites; and (3) that NEAs are not compositionally similar to OCs, implying that they are not the most likely parent bodies of those meteorites, as has been widely believed. To explain their apparently fresh surfaces (NEAs are on average less red than MBs), a combination of composition and size distribution (NEAs have diameters of some kilometres) should be invoked. Dynamical models applied to our sample of NEAs indicate that most of them originate in the inner part of the main belt, as expected.

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“…Our models of binary asteroids were based on physical properties of several objects derived by Pravec et al (2006). A typical binary NEA consists of a fast rotating (2-3 hr), not very elongated primary (lightcurve amplitudes 0.08-0.2 mag), and of a secondary with the size 0.2-0.5 of the primary.…”

Section: Asynchronous Binary Neasmentioning

confidence: 99%

Physical models of asteroids from sparse photometric data

et al. 2006

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Abstract. We present an overview of our work on shape and spin state determination of asteroids from photometric data sparse in time. Our results are based on simulations that were performed using realistic shape and light-scattering models and time sequences that will be provided by Pan-STARRS (Panoramic Survey Telescope and Rapid Response System). We show some typical examples of physical model reconstruction of main belt and near-Earth asteroids and discuss the lightcurve inversion of slow and fast rotators, binary asteroids and tumbling asteroids. We emphasize the scientific potential of sparse photometric data to produce models of a large number of asteroids within the next few years.

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Photometric survey of binary near-Earth asteroids

Cited by 294 publications

References 41 publications

NEA rotations and binaries

NEA rotations and binaries

Observations, compositional, and physical characterization of near-Earth and Mars-crosser asteroids from a spectroscopic survey

Physical models of asteroids from sparse photometric data

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