Strong Erosion-Driven Nongravitational Effects in Orbital Motions of the   Kreutz Sungrazing System's Dwarf Comets
  We investigate the relationships among the angular orbital elements --- the longitude of the ascending node, Omega, the inclination, i, and the argument of perihelion, omega --- of the Kreutz system's faint, dwarf sungrazers observed only with the SOHO/STEREO coronagraphs; their published orbits were derived using a parabolic, purely gravitational approximation. In a plot of i against Omega the bright Kreutz sungrazers (such as C/1843 D1, C/1882 R1, C/1963 R1, etc.) fit a curve of fixed apsidal orientation, whereas the dwarf members are distributed along a curve that makes with the apsidal curve an angle of 15 deg. The dwarf sungrazers' perihelion longitude is statistically invariable, but their perihelion latitude increases systematically with Omega. We find that this trend can be explained by a strong erosion-driven nongravitational acceleration normal to the orbit plane, confirmed for several test dwarf Kreutz sungrazers by orbital solutions with nongravitational terms incorporated directly in the equations of motion on a condition of fixed apsidal orientation. Proceeding in three steps, we first apply Marsden et al.'s standard formalism, solving for the normal acceleration only, and eventually relax additional constraints on the nongravitational law and the acceleration's radial and transverse components. The resulting nongravitational accelerations on the dwarf sungrazers exceed the maximum for catalogued comets in nearly-parabolic orbits by up to three orders of magnitude, topping in exceptional cases the Sun's gravitational acceleration! A mass-loss model suggests that the dwarf sungrazers' nuclei fragment copiously and their dimensions diminish rapidly near the Sun, implying the objects' imminent demise shortly before they reach perihelion. 
Zdenek Sekanina and Rainer Kracht
astro-ph.EP