Neowise Observations of Near-Earth Objects: Preliminary Results

Mainzer, Amy; Grav, T.; Bauer, J. M.; Masiero, J.; McMillan, R. S.; Cutri, R. M.; Walker, R. G.; Wright, E. L.; Eisenhardt, Peter; Tholen, David J.; Spahr, T. B.; Jedicke, Robert; Denneau, L.; DeBaun, E.; Elsbury, D.; Gautier, T. N.; Gomillion, S.; Hand, Emma; Mo, Wenli; Watkins, J. A.; Wilkins, Ashlee; Bryngelson, Ginger; Molina, Antonio C. Perdomo; Desai, S.; Camus, M. Gómez; Hidalgo, Sebastián L.; Konstantopoulos, I. S.; Larsen, Jeffrey A.; Maleszewski, C.; Malkan, Matthew A.; Mauduit, Jean‐Christophe; Mullan, B.; Olszewski, Edward W.; Pforr, Janine; Saro, A.; Scotti, J. V.; Wasserman, L. H.

doi:10.1088/0004-637x/743/2/156

Cited by 352 publications

(339 citation statements)

References 54 publications

(56 reference statements)

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“…Since the fitted beaming parameter values correlate with the phase angle of the observation, α (Delbo' et al 2003;Wolters & Green 2009), it is customary to use a default value (η d ) based on the average of particular asteroid populations whenever it is not possible to fit it (two or more thermal bands are required to have the necessary degree of freedom). An average value of 1.4 was found for NEAs (Mainzer et al 2011a), 1.2 for Mars-crossing asteroids (Alí-Lagoa & Delbo' 2017), 1.0 for MBAs (Masiero et al 2011), and 0.77 for Hildas and Jupiter Trojans ). Here we considered our sample's statistics to choose a default value of η as a function of α.…”

Section: Thermal Modellingmentioning

confidence: 95%

“…This technique, called radiometry, has been the major contributor of asteroid diameters since the 1980s, when the Infrared Astronomical Satellite (IRAS) allowed two thousand asteroid diameters to be determined (Tedesco 1986;Tedesco et al 2002b). After a modest addition of observations of approximately 150 more asteroids by the Midcourse Space Experiment (MSX) in the 1990s (Tedesco et al 2002a), there has been two major space-based all-sky surveys at thermal infrared wavelengths in the last ten years: AKARI (Murakami et al 2007) and WISE/NEOWISE (Wright et al 2010;Mainzer et al 2011a). Usui et al (2011), henceforth U11, used the 9-and 18-µm AKARI all-sky fluxes to produce the Asteroid catalogue using AKARI (AcuA), comprising 5000 asteroid diameters and visible geometric albedos based on an empirical calibration of the standard thermal model (STM) (see e.g.…”

Section: Introductionmentioning

confidence: 99%

“…If AKARI doubled the IRAS catalogue in terms of numbers, WISE/NEOWISE increased the number by two orders of magnitude, providing observations of hundreds of near-Earth asteroids (NEAs) (Mainzer et al 2011a), more than a hundred thousand MBAs (Masiero et al 2011), and thousands of outer A&A proofs: manuscript no. akari_NEATM_arxiv MBAs and Jupiter Trojans .…”

Section: Introductionmentioning

confidence: 99%

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The AKARI IRC asteroid flux catalogue: updated diameters and albedos

Alí-Lagoa

Müller

Usui

et al. 2018

A&A

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The AKARI IRC All-sky survey provided more than twenty thousand thermal infrared observations of over five thousand asteroids. Diameters and albedos were obtained by fitting an empirically calibrated version of the standard thermal model to these data. After the publication of the flux catalogue in October 2016, our aim here is to present the AKARI IRC all-sky survey data and discuss valuable scientific applications in the field of small body physical properties studies. As an example, we update the catalogue of asteroid diameters and albedos based on AKARI using the near-Earth asteroid thermal model (NEATM). We fit the NEATM to derive asteroid diameters and, whenever possible, infrared beaming parameters. We fit groups of observations taken for the same object at different epochs of the survey separately, so we compute more than one diameter for approximately half of the catalogue. We obtained a total of 8097 diameters and albedos for 5170 asteroids, and we fitted the beaming parameter for almost two thousand of them. When it was not possible to fit the beaming parameter, we used a straight line fit to our sample's beaming parameter-versus-phase angle plot to set the default value for each fit individually instead of using a single average value. Our diameters agree with stellar-occultation-based diameters well within the accuracy expected for the model. They also match the previous AKARI-based catalogue at phase angles lower than 50 degrees, but we find a systematic deviation at higher phase angles, at which near-Earth and Mars-crossing asteroids were observed. The AKARI IRC All-sky survey is an essential source of information about asteroids, especially the large ones, since, it provides observations at different observation geometries, rotational coverages and aspect angles. For example, by comparing in more detail a few asteroids for which dimensions were derived from occultations, we discuss how the multiple observations per object may already provide three-dimensional information about elongated objects even based on an idealised model like the NEATM. Finally, we enumerate additional expected applications for more complex models, especially in combination with other catalogues.

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Section: Thermal Modellingmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The AKARI IRC asteroid flux catalogue: updated diameters and albedos

Alí-Lagoa

Müller

Usui

et al. 2018

A&A

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“…The thermal inertia of 1950 DA was determined using archival WISE thermal-infrared observations, which were obtained on 12-13 July 2010 UT during the WISE All-Sky survey 15 were taken, and was only detected at 3-σ levels or greater in the W3 (11 μm) and W4 (22 μm) channels. Additionally, we only used data points that repeatedly sampled common rotation phases of 1950 DA to ensure consistency, and to avoid outliers, within the data set.…”

Section: Analysis Of Wise Thermal-infrared Observationsmentioning

confidence: 99%

Cohesive forces prevent the rotational breakup of rubble-pile asteroid (29075) 1950 DA

Rozitis

MacLennan

Emery

2014

Nature

177

137

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Space missions 1 and ground-based observations 2 have shown that some asteroids are loose collections of rubble rather than solid bodies. The physical behavior of such 'rubble pile' asteroids has been traditionally described using only gravitational and frictional forces within a granular material 3 . Cohesive forces in the form of small van der Waals forces between constituent grains have been recently predicted to be important for small rubble piles (10-kilometer-sized or smaller), and can potentially explain fast rotation rates in the small asteroid population 4-6 . Hitherto, the strongest evidence came from an analysis of the rotational breakup of main belt comet P/2013 R3 (ref. 7), although that was indirect and poorly constrained by present observations. Here we report that the kilometer-sized asteroid (29075) 1950 DA 8 is a rubble pile that is rotating faster than that allowed by gravity and friction. We find that cohesive forces are required to prevent surface mass shedding and structural failure, and that the strength of the forces are comparable to, though somewhat less than, that of lunar regolith.It is possible to infer the existence of cohesive forces within an asteroid by determining if it is a rubble pile with insufficient self-gravity to prevent rotational breakup by centrifugal forces. One of the largest known candidates is near-Earth asteroid 1950 DA (mean diameter of 1.3 km; ref.8), as it has a rotation period of 2.1216 hr that is just beyond the critical spin limit of ~2.2 hr estimated for a cohesionless asteroid 9 . A rubble pile structure and the degree of self-gravity can be determined by a bulk density measurement, which can be acquired through model-tomeasurement comparisons of Yarkovsky orbital drift 10 . This drift arises on a rotating asteroid with non-zero thermal inertia, and is caused by the delayed thermal emission of absorbed sunlight, which applies a small propulsion force to the asteroid's afternoon side. Thermalinfrared observations can constrain the thermal inertia value 11 , and precise astrometric position measurements conducted over several years can constrain the degree of Yarkovsky orbital drift 2 . Recently, the orbital semimajor axis of 1950 DA has been observed to be decreasing at a rate of 44.1 ± 8.5 m yr -1 because of the Yarkovsky effect 12 , which indicates that the asteroid's sense of rotation must be retrograde. Using the Advanced Thermophysical Model 13,14 , in combination with the retrograde radar shape model 8 , archival WISE thermal-infrared data 15 (Extended Data Table 1, and Extended Data Figs 1 and 2), and orbital state 12 , we determine the thermal inertia and bulk density of 1950 DA (Methods). The thermal inertia value is found to be remarkably low at 24 +20 / -14 J m -2 K -1 s -1/2 , which gives a corresponding bulk density of 1.7 ± 0.7 g cm -3 ( Fig. 1 and Extended Data Fig. 3). This bulk density is much lower than the minimum value of 3.5 g cm -3 required to prevent loss of surface material by centrifugal forces (Fig. 2).Spectral observations of 1950...

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“…Initially limited in number by practical constraints on ground-based observations, thermal observations of Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Table 3 is available in electronic form at http://www.aanda.org asteroids have quickly expanded to large surveys, such as IRAS in 1983 (2200 objects in 1983, Tedesco et al 2002), AKARI in 2006-2007 (about 5000 objects, Usui et al 2013), Warm Spitzer ExploreNEO since 2009 (600 near-Earth objects, Trilling et al 2012), and WISE/NEOWISE in 2009-2010, which observed over 150 000 small bodies at 3.4, 4.6, 12, and 22 μm, including some 100 000 main-belt asteroids (Masiero et al 2011), over 400 NEOs (Mainzer et al 2011a), and about 2000 Trojans ).…”

Section: Introductionmentioning

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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Neowise Observations of Near-Earth Objects: Preliminary Results

Cited by 352 publications

References 54 publications

The AKARI IRC asteroid flux catalogue: updated diameters and albedos

The AKARI IRC asteroid flux catalogue: updated diameters and albedos

Cohesive forces prevent the rotational breakup of rubble-pile asteroid (29075) 1950 DA

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

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