Comet Encke

Short-period comets these display a strong tendency for their farthest point from the sun (aphelia) to coincide with a giant planet s orbital radius, so that we can distinguish so-called comet families . The Jupiter family of comets is the largest and numbers around 70 comets. The shortest orbital period known is that of the short-period comet Encke—about 3.3 years. 

Water abundances for 7 comets for which O and OH abundances are now available are given in Table 1. The comets with eccentricities near 1 which have probably been on one of their first close perihelion passages (Kohoutek is the only new comet in this list) have much larger H O productions than the short periodic comets Encke and Bradfield (periods 3.3 years and 250 years resp.). This result agrees with the icy conglomerate model. 

Not all space missions to comets have been as successful as Stardust and Deep Space 1. For example, NASA s CONTOUR (Comet Nucleus Tour), launched on July 3, 2002, was designed to rendezvous with and study Comet Encke on November 12, 2003, and Comet Schwassmann-Wachmann 3 on June 18, 2006. All contact was lost with CONTOUR on August 15, 2002, however, and the mission was canceled. 

Figure 3. The diaphragm dependence of polarization for comets - Encke, (LINEAR), - A2 (LINEAR), V - S4 (LINEAR), n - West, X - Hale-Bopp.

The first echoes from a near-Earth asteroid (1566 Icarus) were detected in 1968 it would be nearly another decade before the first radar detection of a main-belt asteroid (1 Ceres in 1977), to be followed in 1980 by the first detection of echoes from a comet (Encke). During 1972 and 1973, detection of 13-cm-wavelength radar echoes... 

Whipple, F. (1950). A comet model. I. The acceleration of Comet Encke. Astrophysical Journal, 111, 375-94. 

This probe was launched primarily to study two comets, Encke and Schwassmann-Wachmann. It employed five layers of Nextel and Kevlar to protect against impacts from the comet tail. The total thickness of the protections was 25 cm. 

OH is the only coma constituent which has been found in the ultraviolet, in the optical and in the microwave region. Its two hyperfine transitions at 18 cm (1665 and 1667 MHz) have been identified in 7 recent comets, among them the two periodic comets d Arrest and Encke. Generally, the line intensities were in agreement with the assumption of ultraviolet pumping by the solar radiation. This model did, however, not fit to the observations of the two periodic comets. Possibly, this is a... 

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