Physical Properties of Asteroid (308635) 2005 YU55 derived from multi-instrument infrared observations during a very close Earth-Approach

Abstract

The near-Earth asteroid (308635) 2005 YU55 is a potentially hazardous asteroid which was discovered in 2005 and passed Earth on November 8th 2011 at 0.85 lunar distances. This was the closest known approach by an asteroid of several hundred metre diameter since 1976 when a similar size object passed at 0.5 lunar distances. We observed 2005 YU55 from ground with a recently developed mid-IR camera (miniTAO/MAX38) in N- and Q-band and with the Submillimeter Array (SMA) at 1.3 mm. In addition, we obtained space observations with Herschel/PACS at 70, 100, and 160 micron. Our thermal measurements cover a wide range of wavelengths from 8.9 micron to 1.3 mm and were taken after opposition at phase angles between -97 deg and -18 deg. We performed a radiometric analysis via a thermophysical model and combined our derived properties with results from radar, adaptive optics, lightcurve observations, speckle and auxiliary thermal data. We find that (308635) 2005 YU55 has an almost spherical shape with an effective diameter of 300 to 312 m and a geometric albedo pV of 0.055 to 0.075. Its spin-axis is oriented towards celestial directions (lam_ecl, beta_ecl) = (60 deg +/- 30deg, -60 deg +/- 15 deg), which means it has a retrograde sense of rotation. The analysis of all available data combined revealed a discrepancy with the radar-derived size. Our radiometric analysis of the thermal data together with the problem to find a unique rotation period might be connected to a non-principal axis rotation. A low to intermediate level of surface roughness (r.m.s. of surface slopes in the range 0.1 - 0.3) is required to explain the available thermal measurements. We found a thermal inertia in the range 350-800 Jm^-2s^-0.5K^-1, very similar to the rubble-pile asteroid (25143) Itokawa and indicating a mixture of low conductivity fine regolith with larger rocks and boulders of high thermal inertia on the surface.

arXiv commentAccepted for publication in Astronomy & Astrophysics, 12 pages, 10 figures

References in corpus (8)

• Thermal inertia of near-Earth asteroids and implications for the magnitude of the Yarkovsky effect
• "TNOs are Cool": A survey of the trans-Neptunian region X. Analysis of classical Kuiper belt objects from Herschel and Spitzer observations
• Thermo-physical properties of 162173 (1999 JU3), a potential flyby and rendezvous target for interplanetary missions
• Thermal infrared observations of the Hayabusa spacecraft target asteroid 25143 Itokawa
• Physical Properties of OSIRIS-REx Target Asteroid (101955) 1999 RQ36 derived from Herschel, ESO-VISIR and Spitzer observations
• (1173) Anchises - Thermophysical and Dynamical Studies of a Dynamically Unstable Jovian Trojan
• 65 Cybele in the thermal infrared: Multiple observations and thermophysical analysis
• Thermal infrared observations of near-Earth asteroid 2002 NY40

Cited by in corpus (17)

• Asteroid thermophysical modeling
• Volumes and bulk densities of forty asteroids from ADAM shape modeling
• NEOWISE Reactivation Mission Year One: Preliminary Asteroid Diameters and Albedos
• Thermophysical modeling of main-belt asteroids from WISE thermal data
• (25143) Itokawa: The Power of Radiometric Techniques for the Interpretation of Remote Thermal Observations in the Light of the Hayabusa Rendezvous Results
• SsODNet: The Solar system Open Database Network
• Thermal Infrared Observations of Asteroid (99942) Apophis with Herschel
• Constraining the Physical Properties of Near-Earth Object 2009 BD
• Low-speed Impact Simulations into Regolith in Support of Asteroid Sampling Mechanism Design I.: Comparison with 1-g Experiments
• The Pointing System of the Herschel Space Observatory. Description, Calibration, Performance and Improvements
• Physical characterisation of near-Earth asteroid (1620) Geographos. Reconciling radar and thermal-infrared observations
• Thermal Tomography of Asteroid Surface Structure
• Small Bodies: Near and Far Database for thermal infrared observations of small bodies in the Solar System
• Size-dependent modification of asteroid family Yarkovsky V-shapes
• Space-Based Thermal Infrared Studies of Asteroids
• The impact of asteroid shapes and topographies on their reflectance spectroscopy
• Large Halloween Asteroid at Lunar Distance