W. Mo's scientific contributionswhile working at Johns Hopkins University (Baltimore, United States) and other institutions
- Abstract: The NEOWISE dataset offers the opportunity to study the variations in albedo for asteroid classification schemes based on visible and near-infrared observations for a large sample of minor planets. We have determined the albedos for nearly 1900 asteroids classified by the Tholen, Bus and Bus-DeMeo taxonomic classification schemes. We find that the S-complex spans a broad range of bright albedos, partially overlapping the low albedo C-complex at small sizes. As expected, the X-complex covers... Show More
- Abstract: We have combined the NEOWISE and Sloan Digital Sky Survey data to study the albedos of 24,353 asteroids with candidate taxonomic classifications derived using Sloan photometry. We find a wide range of moderate to high albedos for candidate S-type asteroids that are analogous to the S-complex defined by previous spectrophotometrically-based taxonomic systems. The candidate C-type asteroids, while generally very dark, have a tail of higher albedos that overlaps the S types. The albedo... Show More
- Abstract: With the NEOWISE portion of the Wide-field Infrared Survey Explorer (WISE) project, we have carried out a highly uniform survey of the near-Earth object (NEO) population at thermal infrared wavelengths ranging from 3 to 22 μm, allowing us to refine estimates of their numbers, sizes, and albedos. The NEOWISE survey detected NEOs the same way whether they were previously known or not, subject to the availability of ground-based follow-up observations, resulting in the discovery of more than... Show More
Publications citing this author (173)
[Show abstract] [Hide abstract] ABSTRACT: This study addresses thermal modeling of asteroids with a new derivation of the Near Earth Asteroid Thermal (NEATM) model which correctly accounts for the presence of reflected sunlight in short wave IR bands. Kirchhoff's law of thermal radiation applies to this case and has important implications. New insight is provided into the eta parameter in the NEATM model and it is extended to thermal models besides NEATM. The role of surface material properties on eta is examined using laboratory spectra of meteorites and other asteroid compositional proxies; the common assumption that emissivity e=0.9 in asteroid thermal models may not be justified and can lead to misestimating physical parameters. In addition, indeterminacy in thermal modeling can limit its ability to uniquely determine temperature and other physical properties. A new curve fitting approach allows thermal modeling to be done independent of visible band observational parameters such as the absolute magnitude H. These new thermal modeling techniques are applied to observational data for selected asteroids from the WISE/NEOWISE mission. The previous NEOWISE analysis assumes Kirchhoff's law does not apply. It also deviates strongly from established statistical practice and systematically underestimates the sampling error inherent in observing potentially irregular asteroids from a finite sample of observations. As a result, the new analysis finds asteroid diameter and other physical properties that have large differences from published NEOWISE results, with greatly increased error estimates. NEOWISE results have a claimed +/-10% accuracy for diameter estimates, but this is unsupported by any calculations and undermined by irregularities in the NEOWISE results. ABSTRACT CONTINUED IN PDF...
- This choice is inconsistent with the approach taken for asteroids that lack enough bands dominated by thermal emission to fit for í µí¼. In such cases, the NEOWISE authors assign a value of í µí¼ that is taken from the average value found for the same group; í µí¼ = 1.0 for main belt asteroids (Masiero et al., 2011), í µí¼ = 0.77 for Hildas (Grav et al., 2011b), í µí¼ = 1.4 for NEO (Mainzer et al., 2011b). This method allows for a paradoxical situation in which í µí¼ can be forced to have the same value across thousands of different asteroids in a group, but allowed to vary across the observational epochs only days apart for an individual asteroid.
[Show abstract] [Hide abstract] ABSTRACT: The so-called Nysa-Polana complex of asteroids is a diverse and widespread group. It appears to be two overlapping families of different asteroid taxonomies: (44) Nysa is an E-type asteroid with the lowest number in the midst of a predominantly S-type cluster and (142) Polana is a B-type asteroid near the low-albedo B- and C-type cluster. Using the data from the Wide-field Infrared Survey Explorer (WISE) mission we have re-analyzed the region around the Nysa-Polana complex in the inner Main Belt, focusing on the low-albedo population. (142) Polana does not appear to be a member of the family of low-albedo asteroids in the Nysa-Polana complex. Rather, the largest is asteroid (495) Eulalia. This asteroid has never before been linked to this complex for an important dynamical reason: it currently has a proper eccentricity slightly below the range of most of the family members. However, its orbit is very close to the 3:1 mean motion resonance with Jupiter and is in a weak secular resonance. We show that its osculating eccentricity varies widely on short timescales and the averaged value diffuses over long timescales. The diffusive orbit, low-albedo, taxonomic similarity and semimajor axis strongly suggests that despite its current proper eccentricity, (495) Eulalia could have recently been at an orbit very central to the family. Hierarchical Clustering Method tests confirm that at an eccentricity of e=0.15, (495) Eulalia could be the parent of the family. The ``Eulalia family'' was formed between 900--1500 Myr ago, and likely resulted from the breakup of a 100--160 km parent body. There is also compelling evidence for an older and more widespread primitive family in the same region of the asteroid belt parented by asteroid (142) Polana.
- rger Nysa - Polana complex ( NPC ) - which appears to be two overlapping asteroid families of different asteroid taxonomies . Their overlapping nature has made detailed study difficult , but now the large database of albedos measured by the WISE mission has made a study of each of the two componenets of the family possible ( Masiero et al . 2011 ; Mainzer et al . 2011 ) .