Periodic Comets

active aphelion Aquarid asteroid belt astrometry Astron Astrophys asymmetry Bailey capture Chiron close encounters coma comet Austin comet belt comet Halley cometary computed detected Duncan dust ejection dust mantling dust tail earth-crossing encounters with Jupiter energy estimate Everhart evolution of comets Fernandez Figure giant comet grains Halley Halley-type comets heliocentric distance IGNACIO FERRIN images inclination inner core integrations interplanetary dust cloud JF comets Jupiter-family comets Kresak Kuiper belt lifetime long-period comets loss rate mass loss meteor orbit meteoroids near-Earth asteroids nongravitational force nuclear magnitudes nucleus objects observed Oort cloud orbital elements orbital evolution orbital period P/Encke P/Halley parameters particle perihelion distance period comets perturbation distributions physical planets plot population present Quinn radius range Rickman sample Saturn scale length semi-major axis short-period comets showers simulation solar maximum solar system solar wind Taurid telescope Tisserand invariant Valsecchi values velocity