The optical properties of asteroids depend on the properties of the grains on their surfaces. Spectroscopic observations can be used to determine the composition and evolution of asteroids from Earth. This is mostly done in visible and infrared wavelengths. Asteroid properties in the ultraviolet (<300 nm) are poorly studied because Earth’s atmosphere absorbs UV light, and most instruments have poor sensitivity in this regime.

Over the last two years, we have used the Swift space telescope to fill this gap. We observed 16 different asteroids. These include the famous asteroids Vesta, Ceres, Lutetia, and Eros (space craft targets), and many objects that are typical for asteroid families and taxonomical classes. We are currently interpreting the results of the Swift asteroid catalogue.


  1. ‘Ultraviolet Spectroscopy of Asteroid (4) Vesta’, J.-Y. Li, D. Bodewits, et al. 2011, Icarus [ArXiv]

  2. Swift observations of YU55: CBET #2937

  3. “Collisional Excavation of Asteroid (596) Scheila” - D. Bodewits, M.S. Kelley, J.Y. Li, W.B. Landsman, S. Besse and M.F. A’Hearn, The Astrophysical Journal Letters 733, L3, 2011 (ArXiv)


LEFT: Using a special observing technique Swift was able to capture the small asteroid YU55 when it zipped by Earth. By comparing its UV colors and phase curve with our other asteroid observations we identified YU55 as a C-type asteroid. This class of very dark asteroids resides mostly in the outer Main Belt.


  1. (1)Ceres

  2. (2)Pallas;

  3. (3)Juno

  4. (4)Vesta

  5. (6)Hebe

  6. (7)Iris;

  7. (8)Flora

  8. (10)Hygiea

  9. (15)Eunomia

  10. (20)Massalia

  11. (21)Lutetia

  12. (44)Nysa

  13. (349)Dembowska

  14. (433)Eros

  15. (596)Scheila

2005 YU55