Near-Earth asteroid (3200) Phaethon: Characterization of its orbit, spin state, and thermophysical parameters

Abstract

Context. The near-Earth asteroid (3200) Phaethon is an intriguing object: its perihelion is at only 0.14 au and is associated with the Geminid meteor stream. Aims. We aim to use all available disk-integrated optical data to derive a reliable convex shape model of Phaethon. By interpreting the available space-and ground-based thermal infrared data and Spitzer spectra using a thermophysical model, we also aim to further constrain its size, thermal inertia, and visible geometric albedo. Methods. We applied the convex inversion method to the new optical data obtained by six instruments and to previous observations. The convex shape model was then used as input for the thermophysical modeling. We also studied the long-term stability of Phaethon's orbit and spin axis with a numerical orbital and rotation-state integrator.Results. We present a new convex shape model and rotational state of Phaethon: a sidereal rotation period of 3.603958(2) h and ecliptic coordinates of the preferred pole orientation of (319 • , −39 • ) with a 5 • uncertainty. Moreover, we derive its size (D = 5.1 ± 0.2 km), thermal inertia (Γ = 600 ± 200 J m −2 s −1/2 K −1 ), geometric visible albedo (p V = 0.122 ± 0.008), and estimate the macroscopic surface roughness. We also find that the Sun illumination at the perihelion passage during the past several thousand years is not connected to a specific area on the surface, which implies non-preferential heating.

Asteroid (3200) Phaethon: Colors, Phase Curve, Limits on Cometary Activity, and Fragmentation

“…This is because the approximate plane containing the preferred and alternate pole solutions is roughly perpendicular to our line-of-sight during the asteroid's close approach, and so an Earth-bound observer's sub-latitude crosses Phaethon's equator at about the same time in either case (e.g. 13 hours later for the Hanuš et al (2016) alternate pole solution). As a result, our finding of a color difference with sub-latitude would still stand, but the exact distribution on the asteroid's surface would be different.…”

“…Ohtsuka et al (2009) andAnsdell et al (2014) found that the northern latitudes of Phaethon would be preferentially heated and bluer in B-V, using the pole solution of Krugly et al (2002). However, Hanuš et al (2016) argued, using an updated pole solution, that Phaethon has not suffered preferential heating over the last thousands of years.…”

“…(Animated figure) Viewing geometry from Earth through the close approach of Phaethon in December 2017. On the left is the pole solution adopted here(Hanuš et al 2018), on the right is an alternate pole solution fromHanuš et al (2016). Green indicates times where photometric data was taken.…”

Revisiting the Advanced Thermal Physical Model: New Perspectives on Thermophysical Characteristics of (341843) 2008 EV5 from Four-bandWISEData with the Sunlight-reflection Model

“…Here we adopt the initial orbital elements of nominal orbit and their uncertainties for EV5 from the Minor Planet Center (MPC)(see Table 3). Similar to Hanuš et al (2016), we generated 1000 orbital clones except for the nominal orbit. All the orbital elements in each clone was yielded within the uncertainties given in Table 3.…”

NEOWISE Reactivation Mission Year Three: Asteroid Diameters and Albedos

“…NEATM is by necessity a simple approximation of the real thermal behavior of asteroid surfaces; more detailed thermophysical modeling (e.g. , Spencer 1990;Lagerros 1997;Wright 2007;Alí-Lagoa et al 2014;Koren et al 2015;Hanuš et al 2016;Nugent et al 2017) can provide improved constraints on the physical and thermal properties of an asteroid if multiple viewing geometries are available, though at the expense of greatly increased computation time. We provide NEATMderived physical properties here as a springboard for more detailed modeling of targets of interest.…”