Kiana McFadden, University of Arizona
In oral session Asteroids: Missions, Mission Targets, Surveys on Tuesday, October 8, 2024, 4:24-4:36pm MT, Program Number: 212.04
Updated Diameters and Albedos for the Main Belt Asteroids Using WISE/NEOWISE Data
Kiana McFadden1, Amy Mainzer2, Joseph Masiero3, James Bauer4, Roc Cutri5, Dar Dahlen5, Frank Masci6, Jana Pittichova7, Edward Wright2
1Lunar and Planetary Laboratory/University of Arizona, Tucson, AZ, 2UC, Los Angeles, Los Angeles, CA, 3Caltech/IPAC, Pasadena, CA, 4Dept. of Astronomy, University of Maryland, College Park, MD, 5Caltech, IPAC, Pasadena, CA, 6IPAC/Caltech, Pasadena, CA, 7Jet Propulsion Laboratory, Pasadena, CA
Small bodies allow us to probe the processes that occurred during the formation of our solar system more than 4 billion years ago. To infer the nature of the primordial population, we can analyze the present-day main belt asteroid population and create models of how it evolved under collisional, gravitational, and non-gravitational forces (e.g., Bottke et al. 2005, Holsapple et al. 2022). We can use what we know about the asteroids’ current physical properties as constraints on these formation models. It is now possible to compute these physical properties for a large sample of the population using data from the Wide-field Infrared Survey Explorer (WISE)/Near-Earth Object WISE (NEOWISE) mission (Wright et al. 2010, Mainzer et al. 2011, 2014). WISE had four channels (3.4, 4.6, 12, and 22 um) during the fully cryogenic phase of its mission. After it was reactivated, it was renamed NEOWISE and operated with the two shorter wavelength channels (3.4 and 4.6 um, denoted W1 and W2).
Several studies have utilized these data to determine the diameters and albedos for a subset of asteroids in the main belt and beyond (Masiero et al. 2011, 2014). Presently, NEOWISE has collected an additional 10 years of data since these studies were conducted. Because of these additional observations, the main belt asteroids now have improved orbits and more mid-infrared measurements. The additional data allows us to determine the infrared albedo at 3.4 um for many more objects, and we can compare this to the visual albedo. In many cases, we can compute a slope for objects with featureless spectra, and we can distinguish between objects with flat slopes or red slopes (i.e., C-types, P-types, and D-types; Grav et al. 2012, 2012).
We used the Near-Earth Asteroid Thermal Model (NEATM; Harris 1998) to determine the physical parameters of the main belt asteroids. With NEATM, we assume that an asteroid is a non-rotating sphere, and there is no emission on the night side. NEATM uses a beaming parameter as a proxy for surface roughness and thermal inertia. We computed thermal models for ~160,000 main belt asteroids. We present preliminary results of sizes, albedos, and thermal fit parameters from this study of main belt asteroids.
References:
- Bottke, W. et al. Icarus, 179, 63 (2005).
- Grav et al. ApJ, 759, 49 (2012).
- Grav et al. ApJ,744, 197 (2012).
- Harris, A., Icarus, 131, 291 (1998).
- Holsapple, K. et al. Planet. Space Si, (2022).
- Mainzer, A. et al. ApJ, 731, 53 (2011).
- Mainzer, A. et al. ApJ, 792, 30 (2014).
- Masiero, J et al. ApJ,741,68 (2011).
- Masiero, J. et al. ApJ, 791, 121 (2014).
- Wright, E. L. et al. AJ, 140, 1868 (2010).