Chapter 23 Section 4Minor Members of Our Solar System

AsteroidsComets

Meteoroids/Meteors/MeteoritesKuiper BeltOort Cloud

Asteroids• Small rocky bodies; irregular

shape• Lie between orbits of Mars &

Jupiter (asteroid belt)• Orbital period of 3-6 years

– Some asteroids have very eccentric orbits & travel close to the Sun.

– Others (larger) regularly pass close to Earth & Moon

• Largest asteroid: Ceres—1,000 km diameter

PHAs (Potentially Hazardous Asteroids)

Why track asteroid paths?

NASA Capture Pet Asteroid?

Location of Asteroids

Comets• Rocky, metallic material held together by frozen gases (water, ammonia, methane, CO2, and CO)

• Elongated orbits (far beyond Pluto)– Orbital period of most hundreds of thousands of years– Some less than 200 years and encounter inner solar system

• Anatomy of a comet:– Coma-glowing head produced as frozen gases vaporized– Nucleus-located in the coma; icy– Tail-typically forms as approach Sun (can extend millions of km); always points AWAY from Sun in curved manner

• Radiation pressure—forms dust tail• Solar wind– forms ionized (gas) tail (mainly CO)

Space Debris Song

Halley’s Comet-Periodic comet-Passes Earth every 76 years-Last pass: 1986-Next pass: 2061

Comet Ison-Originated from Oort Cloud-Most agree it did not survive orbit around Sun

Kuiper Belt & Oort CloudKuiper Belt

• Birthplace of short orbital period comets; nearly circular orbits roughly in same plane of planets

• Located beyond Neptune• Most comets we see are Kuiper

Belt comets

Oort Cloud• Birthplace of long orbital

period comets; highly eccentric orbits; not confined to plane of solar system

• “3-D shell” around solar system

• Very rarely do we observe an Oort Cloud comet

Closer Look at the Kuiper Belt

Meteoroids• Meteoroid: small solid particle in space; made of iron

– Originate from: interplanetary debris, asteroid belt, or remains of a comet

• Meteor: meteoroids that enter Earth’s atmosphere; burn once in atmos.

– Where does light originate?– Meteor showers Earth encounters swarm of meteoroids

traveling same speed/direction link to comets…WHY?

• Meteorite: reaches Earth’s surface– Meteor Crater Winslow, Arizona

• ~50,000 years ago• Originated from asteroid belt• ~26,000 mph prior to impact; 150 ft across• Crater is roughly

– 1 mile wide– 2.4 mile circumference– 550 feet deep