Densities of Solar System Objects from Their Rotational Light Curves

Lacerda, Pedro; Jewitt, David

doi:10.1086/511772

Cited by 131 publications

(148 citation statements)

References 33 publications

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“…Even more interesting is that shape modeling has suggested a density higher than nearly anything else known in the Kuiper belt and consistent with a body almost thoroughly dominated by rock (Rabinowitz et al 2006;Lacerda et al 2008;Lellouch et al 2010). Lacerda & Jewitt (2007) concluded a density of 2.551 g cm −3 and follow up work found consistent values between 2.55 and 2.59 g cm −3 , depending on the model used. Such a rocky body with an icy exterior could be a product of initial differentiation before giant impact and subsequent removal of a significant amount of the icy mantle.…”

Section: Introductionmentioning

confidence: 91%

The Size and Shape of the Oblong Dwarf Planet Haumea

2014

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We use thermal radiometry and visible photometry to constrain the size, shape, and albedo of the large Kuiper belt object Haumea. The correlation between the visible and thermal photometry demonstrates that Haumea's high amplitude and quickly varying optical light curve is indeed due to Haumea's extreme shape, rather than large scale albedo variations. However, the well-sampled high precision visible data we present does require longitudinal surface heterogeneity to account for the shape of lightcurve. The thermal emission from Haumea is consistent with the expected Jacobi ellipsoid shape of a rapidly rotating body in hydrostatic equilibrium. The best Jacobi ellipsoid fit to the visible photometry implies a triaxial ellipsoid with axes of length 1920 x 1540 x 990 km and density 2.6 g cm −3 , as found by Lellouch et al. (2010). While the thermal and visible data cannot uniquely constrain the full non-spherical shape of Haumea, the match between the predicted and measured thermal flux for a dense Jacobi ellipsoid suggests that Haumea is indeed one of the densest objects in the Kuiper belt.

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Section: Introductionmentioning

confidence: 91%

The Size and Shape of the Oblong Dwarf Planet Haumea

2014

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“…Specifically, upon an assumption on the object density (ρ), we used the rotation period P = 2π/ω to calculate ω 2 /(π G ρ), where G is the gravitational constant. When lower than a limit of 0.3742, the latter quantity provides c/a and b/a by interpolation from Chandrasekhar's (1987) tables (see also Lacerda & Jewitt 2007). We considered two density cases (ρ = 1000 and 3000 kg m −3 ) and restricted ourselves to objects with some minimum lightcurve amplitude (Δm min ), considering that lightcurves with lower amplitudes may instead be due to albedo markings on a MacLaurin spheroid.…”

Section: Attempting To Use Rotational Informationmentioning

confidence: 99%

“TNOs are Cool”: A survey of the trans-Neptunian region

Lellouch

Santos-Sanz

Lacerda

et al. 2013

A&A

135

143

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Aims. The goal of this work is to characterize the ensemble thermal properties of the Centaurs / trans-Neptunian population. Methods. Thermal flux measurements obtained with Herschel/PACS and Spitzer/MIPS provide size, albedo, and beaming factors for 85 objects (13 of which are presented here for the first time) by means of standard radiometric techniques. The measured beaming factors are influenced by the combination of surface roughness and thermal inertia effects. They are interpreted within a thermophysical model to constrain, in a statistical sense, the thermal inertia in the population and to study its dependence on several parameters. We use in particular a Monte-Carlo modeling approach to the data whereby synthetic datasets of beaming factors are created using random distributions of spin orientation and surface roughness. Results. Beaming factors η range from values <1 to ∼2.5, but high η values (>2) are lacking at low heliocentric distances (r h < 30 AU). Beaming factors lower than 1 occur frequently (39% of the objects), indicating that surface roughness effects are important. We determine a mean thermal inertia for Centaurs/ TNO of Γ = (2.5 ± 0.5) J m −2 s −1/2 K −1 , with evidence of a trend toward decreasing Γ with increasing heliocentric (by a factor ∼2.5 from 8-25 AU to 41-53 AU). These thermal inertias are 2-3 orders of magnitude lower than expected for compact ices, and generally lower than on Saturn's satellites or in the Pluto/Charon system. Most high-albedo objects are found to have unusually low thermal inertias. Our results suggest highly porous surfaces, in which the heat transfer is affected by radiative conductivity within pores and increases with depth in the subsurface.

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“…These can be used to estimate the density by two methods. By either balancing gravitational and centrifugal forces for an assumed strengthless (rubble pile) body, as applied to asteroids (Pravec et al 2002) and comets (Snodgrass et al 2006), or by assuming a fluid equilibrium shape (i.e., a Jacobi ellipsoid), which may be more appropriate for large icy bodies such as TNOs (Lacerda & Jewitt 2007). The densities of TNOs derived from lightcurves was reviewed by Duffard et al (2009) and Thirouin et al (2010).…”

Section: Rotation and Densitymentioning

confidence: 99%

“…The exception is 2003 SQ 317 , which has a large lightcurve amplitude (Snodgrass et al 2010), implying that it is likely to be a contact binary (therefore the Jacobi ellipsoid model does not hold, Lacerda & Jewitt 2007).…”

Section: Rotation and Densitymentioning

confidence: 99%

“…We exclude Haumea and objects with Δm > 0.9 mag from this calculation: Haumea is not representative of the densities of its family, and objects with very large Δm obey a different relationship between rotational properties and bulk density (Lacerda & Jewitt 2007). Considering the two populations made of the 7 family members and the 64 background TNOs, we obtain a value of Z = 1.276.…”

Section: Rotation and Densitymentioning

confidence: 99%

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Characterisation of candidate members of (136108) Haumea’s family

Carry

Snodgrass

Lacerda

et al. 2012

A&A

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Context. From a dynamical analysis of the orbital elements of trans-Neptunian objects (TNOs), , AJ, 134, 2160 reported a list of candidate members of the first collisional family found among this population, associated with (136 108) Haumea (a.k.a. 2003 EL 61 ). Aims. We aim to distinguish the true members of the Haumea collisional family from interlopers. We search for water ice on their surfaces, which is a common characteristic of the known family members. The properties of the confirmed family are used to constrain the formation mechanism of Haumea, its satellites, and its family. Methods. Optical and near-infrared photometry is used to identify water ice. We use in particular the CH 4 filter of the Hawk-I instrument at the European Southern Observatory Very Large Telescope as a short H-band (H S ), the (J − H S ) colour being a sensitive measure of the water ice absorption band at 1.6 μm. Results. Continuing our previous study headed by Snodgrass, we report colours for 8 candidate family members, including nearinfrared colours for 5. We confirm one object as a genuine member of the collisional family (2003 UZ 117 ), and reject 5 others. The lack of infrared data for the two remaining objects prevent any conclusion from being drawn. The total number of rejected members is therefore 17. The 11 confirmed members represent only a third of the 36 candidates. Conclusions. The origin of Haumea's family is likely to be related to an impact event. However, a scenario explaining all the peculiarities of Haumea itself and its family remains elusive.

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Densities of Solar System Objects from Their Rotational Light Curves

Cited by 131 publications

References 33 publications

The Size and Shape of the Oblong Dwarf Planet Haumea

The Size and Shape of the Oblong Dwarf Planet Haumea

“TNOs are Cool”: A survey of the trans-Neptunian region

Characterisation of candidate members of (136108) Haumea’s family

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