• DOI:10.1086/338093
• Corpus ID: 119337148

Analysis of the First Disk-resolved Images of Ceres from Ultraviolet Observations with the Hubble Space Telescope

@article{Parker2001AnalysisOT,
  title={Analysis of the First Disk-resolved Images of Ceres from Ultraviolet Observations with the Hubble Space Telescope},
  author={Joel Wm. Parker and Sharon A. Stern and Peter C. Thomas and Michel C. Festou and William J. Merline and Eliot F. Young and Richard P. Binzel and Larry Allen Lebofsky},
  journal={The Astronomical Journal},
  year={2001},
  volume={123},
  pages={549 - 557}
}

• J. Parker, S. Stern, +5 authors L. Lebofsky
• Published 10 October 2001
• Physics, Geology
• The Astronomical Journal

We present Hubble Space Telescope Faint Object Camera observations of the asteroid 1 Ceres at near-, mid-, and far-UV wavelengths (λ = 3636, 2795, and 1621 Å, respectively) obtained on 1995 June 25. The disk of Ceres is well resolved for the first time, at a scale of ∼50 km. We report the detection of a large, ∼250 km diameter surface feature for which we propose the name "Piazzi"; however, it is presently uncertain whether this feature is due to a crater, albedo variegation, or other effect. From limb fits to the images, we obtainsemimajor and semiminor axes of R1 = 484.8 ± 5.1 km and R2 = 466.4 ± 5.9 km, respectively, for the illumination-corrected projected ellipsoid. Although albedo features are seen, they do not allow for a definitive determination of the rotational motion and pole position of Ceres, particularly because of the sparse sampling (two epochs) of the 9 hr rotation period. From full-disk integrated albedo measurements, we find that Ceres has a red spectral slope from the mid- to near-UV, and a significant blue slope shortward of the mid-UV. Despite the presence of Piazzi, we detect no significant global differences in the integrated albedo as a function of rotational phase for the two epochs of data we obtained. From Minnaert surface fits to the near- and mid-UV images, we find an unusually large Minnaert parameter of k ≈ 0.9, suggesting a more Lambertian than lunar-like surface.