Identification of water ice on the Centaur 1997 CU26

Science

Volumn 280, Issue 5368, 1998, Pages 1430-1432

  Brown, Robert H ^a   Cruikshank, Dale P ^b   Pendleton, Yvonne ^b   Veeder, Glenn J ^c  

^a UNIVERSITY OF ARIZONA   (United States)

^b NASA AMES RESEARCH CENTER   (United States)

^c CALIFORNIA INSTITUTE OF TECHNOLOGY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ICE;

ABSORPTION; ARTICLE; ASTRONOMY; GRAVITY; INFRARED SPECTROSCOPY; PHOTOCHEMISTRY; PRIORITY JOURNAL;

NASA CENTER ARC; NASA DISCIPLINE EXOBIOLOGY;

HYDROCARBONS; ICE; JUPITER; METHANE; SOLAR SYSTEM; SPECTROPHOTOMETRY, INFRARED; WATER;

ANTHRISCUS SYLVESTRIS;

EID: 0032577292     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.280.5368.1430     Document Type: Article

References (28)

1. Minor Planet Circ. 31010 (1997).
2. M. Duncan, T. Quinn, S. Tremaine, Astrophys. J. Lett. 328, L69 (1988); B. Gladman and M. Duncan, Astron. J. 100, 1680 (1990); M. J. Holman and J. Wisdom, ibid. 105, 1987 (1993); M. Irwin, S. Tremaine, A. Zytkow, ibid. 110, 3082 (1995).
3. M. Duncan, T. Quinn, S. Tremaine, Astrophys. J. Lett. 328, L69 (1988); B. Gladman and M. Duncan, Astron. J. 100, 1680 (1990); M. J. Holman and J. Wisdom, ibid. 105, 1987 (1993); M. Irwin, S. Tremaine, A. Zytkow, ibid. 110, 3082 (1995).
4. M. Duncan, T. Quinn, S. Tremaine, Astrophys. J. Lett. 328, L69 (1988); B. Gladman and M. Duncan, Astron. J. 100, 1680 (1990); M. J. Holman and J. Wisdom, ibid. 105, 1987 (1993); M. Irwin, S. Tremaine, A. Zytkow, ibid. 110, 3082 (1995).
5. M. Duncan, T. Quinn, S. Tremaine, Astrophys. J. Lett. 328, L69 (1988); B. Gladman and M. Duncan, Astron. J. 100, 1680 (1990); M. J. Holman and J. Wisdom, ibid. 105, 1987 (1993); M. Irwin, S. Tremaine, A. Zytkow, ibid. 110, 3082 (1995).
6. D. Jewitt, J. Luu, J. Chen, ibid. 112, 1225 (1996).
7. G. P. Kuiper, in Astrophysics (McGraw-Hill, New York, 1951), pp. 357-424; K. E. Edgeworth, Mon. Not. R. Astron. Soc. 109, 600 (1948).
8. G. P. Kuiper, in Astrophysics (McGraw-Hill, New York, 1951), pp. 357-424; K. E. Edgeworth, Mon. Not. R. Astron. Soc. 109, 600 (1948).
9. 1997 CU26 is in a moderately eccentric orbit of inclination 23.4°, lying mostly between Saturn and Uranus. Its aphelion distance is 18.36 astronomical units (AU), barely inside the orbit of Uranus. Its estimated diameter is 440 km, comparable to Uranus' satellite Miranda and Neptune's satellite Nereid. The orbital period of 1997 CU26 is 62.9 years.
10. s is the K short filter whose passband encompasses the short-wavelength half of the standard K band.
11. D. J. Tholen, in Asteroids II (Univ. of Arizona Press, Tucson, AZ, 1989), pp. 1139-1150; J. F. Bell, B. R. Hawke, P. D. Owensby, M. J. Gaffey, Lunar Planet. Sci. Conf. XIX, 57 (1988).
12. D. J. Tholen, in Asteroids II (Univ. of Arizona Press, Tucson, AZ, 1989), pp. 1139-1150; J. F. Bell, B. R. Hawke, P. D. Owensby, M. J. Gaffey, Lunar Planet. Sci. Conf. XIX, 57 (1988).
13. B. Hapke, in Remote Geochemical Analyses: Elemental and Mineralogical Composition (Cambridge Univ. Press, New York, 1993), pp. 31-41.
14. S. Warren, Appl. Opt. 23, 1206 (1984).
15. O. B. Toon, M. A. Tolbert, B. G. Koehler, A. M. Middlebrook, J. Jordan, J. Geophys Res. 99, 25631 (1994).
16. The optical constants of water ice used here were taken from (9) and shifted in wavelength to agree with (10). The data of (9) were deemed to be more precise in the 1.4-to 2.4-μm wavelength region than those in (10), but the central wavelengths of the absorption bands in (10) corresponded more closely with those of water ice at the 90 to 95 K estimated average present surface temperature of 1997 CU26. This temperature range was calculated assuming a spherical body, a 5 to 20% bolometric bond albedo, instantaneous equilibrium with sunlight, a mean solar zenith angle of √2/π, and a heliocentric distance of 13.7 AU.
17. The optical constants for the red material were derived by assuming a real index of refraction of 1.4 at a wavelength of 1.0 μm and a Lambert absorption coefficient that increased linearly toward longer wavelengths. These quantities were processed through a subtractive Kramers-Kronig algorithm giving the real indices of refraction corresponding to the defined imaginary indices and the real index in the visual. The calculated reflectance for 10-μm grains gives a roughly linear increase in reflectance from 7.5% at 1.0 μm to 9% at 2.5 μm
18. C. Sagan, B. N. Khare, J. S. Lewis, in Satellites, J. A. Burns and M. S. Matthews, Eds. (Univ. of Arizona Press, Tucson, AZ, 1984), pp. 788-807.
19. U. Fink and G. T. Sill, in Comets, L. Wilkening, Ed. (Univ. of Arizona Press, Tucson, AZ, 1982), pp. 164-202.
20. The convolution was done as a direct, discrete, numerical-integral convolution (not as a Fourier convolution). The purpose is to model data obtained at intrinsically lower spectral resolution (with the associated increase in SNR due to the larger spectral bandpass). In contrast to the common practice of binning data, which is mathematically equivalent to a discrete convolution with a square wave, the band-pass of most grating and grism spectrometers is very nearly Gaussian; thus, the result is a much better approximation to spectral data obtained at intrinsically lower spectral resolution.
21. The uncertainties were estimated by propagating the error bars of the high-resolution data directly through the convolution (15). Photon shot noise from the sky background is expected to be the dominant noise source, but, because the contributions of all the noise sources are not known, a correction for the photon shot noise difference expected in the wider bandpass of the convolved data was not included in the calculation.
22. D. P. Cruikshank et al., in preparation.
23. D. P. Cruikshank, in From Stardust to Planetesimals, Y. J. Pendleton and A. G. G. M. Tielens, Eds. (Astronomical Society of the Pacific, San Francisco, CA, 1997).
24. R. H. Brown, D. P. Cruikshank, Y. Pendleton, G. J. Veeder, Science 276, 937 (1997).
25. J. X. Luu, D. C. Jewitt, E. Cloutis, Icarus 109, 133 (1994).
26. J. X. Luu and D. C. Jewitt, Astrophys. J. 494, L117 (1998); D. C. Jewitt and J. X. Luu, in preparation.
27. J. X. Luu and D. C. Jewitt, Astrophys. J. 494, L117 (1998); D. C. Jewitt and J. X. Luu, in preparation.
28. The W. M. Keck Observatory is operated as a scientific partnership between the California Institute of Technology and the University of California. It was made possible by the generous financial support of the W. M. Keck Foundation. The authors acknowledge the assistance of R. Mastrapa at the telescope and the financial support of NASA through the various grants and contracts that support the authors' work.