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The Wide Field Camera (WFC) on the Hubble Space Telescope and the Low Resolution Imaging Spectrograph (LRIS) on the Keck II telescope have been used to image 21 distant dynamically new, long-period (LP) and short-period (SP) Jupiter-family (JF) comet nuclei (near aphelion), as part of a long-term program to search for physical differences between short-period comets and Oort cloud comets. WFC data were obtained on Comets C/1987 H1 (Shoemaker) and C/1984 K1 (Shoemaker) during Cycle 5 (1995 December) and on C/1988 B1 (Shoemaker), C/1987 F1 (Torres), and C/1983 O1 (Cernis) during Cycle 6 (1997 April, May, and June). The HST comets were at heliocentric distances 20.4 4.0 N [ km ] . The SP comets range in radius between 0.34 N [ km ] , with a median value of RN∼1.61 km. The LP comets ranged in size between RN)∝RN−α with α=1.45±0.05, and for nuclei in the range 2–5 km, α=1.91±0.06. Statistical analysis and modeling shows that the slopes of the observed TNO and JF comet distributions are not compatible, suggesting that the intrinsic distribution of JF comet nuclei is a differential a−3.5 power law truncated at small nucleus radii between 0.3 and 2.0 km. |
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