22.2 Comets and Kuiper Belt Objects Roxanne Ryan

Overview Comets – Dynamics of tail – Composition Oort Cloud Kuiper Belt

Model of a Comet Fred Whipple proposed a model which explained most physical characteristics.  Nucleus  Tails  Coma  Halo

Dynamics of Comet Tails Two distinct tails – Dust tail- created by radiation pressure on freed dust grains – Ion tail – interaction of ions in the comet with solar wind and suns magnetic field. Tails are always directed away from the sun.

Composition of Comets Dust tails are white or yellowish due to light scattering off the particles.

Composition of Comets The ion tail is blue because it is rich in CO + ions which absorb and reradiate photons at wavelengths near 420 nm

Robotic Exploration of Comets In March 1986 Whipple’s “dirty-snowball” model was confirmed. July 4, 2004 Deep Impact sent a impactor into Comet Temple 1, allowing scientist to study interior. Comets density is roughly that of powder snow ~600 kg/m 3.

Where do Comets come From? Two types of comets: – Short period: periods of less than 200 year and are found near the ecliptic – Long period: periods greater than 200 years and seemingly random orbits

Kuiper Belt Located 30 – 50 AU from the sun First proposed around 1950 The first KBO was discovered in 1992 By 2006 over 900 had been discovered

Classes of Kuiper Belt Object’s Classical KBO’s – 30 – 50 AU from the sun – Orbital inclination of less than 30˚ – Semi-major axis AU

Classes of Kuiper Belt Object’s Scattered KBO’s – Much higher eccentricity – Greater orbital inclination – Perihelion ~ 35 AU – Source of short period comets

Classes of Kuiper Belt Object’s Resonant KBO’s – KBO’s that are in orbital resonance with Neptune – Resonant Kbo’s with the same 3:2 resonance as Pluto and Charon are called Plutinos

Oort Cloud In 1950 Jan Oort proposed that long period comets originate in a distant distribution of cometary nuclei. Has never been observed, but it’s existence is certain.

Oort Cloud 3, ,00 AU from the sun bodies Total mass ~ 100 solar masses

22.2 Comets and Kuiper Belt Objects Roxanne Ryan