Small objects in the Solar System Meteors, Comets, : we see them without a telescope Asteroids: small rocky objects mostly between Mars and Jupiter – too faint to see without a telescope Kuiper belt objects: even fainter objects beyond Pluto, debris left over from solar system formation Make a dry ice comet as class intro, bring hula hoop, meteor kit Collect HW: reading on asteroids & dinosaurs Image of comet Wild 2, visited by Stardust, return Jan 2006 Image of comet Wild 2, visited by Stardust mission, return Jan 2006

Meteors: debris from comets, chips of asteroids Meteors (shooting stars) can appear at any time, from any direction. Meteor: The bright tail of hot debris from the rock Meteorite: A rock from space that reaches Earth’s surface

Peekskill, NY: October 9, 1992

If a meteor does not burn up completely, and reaches the ground it is a meteorite Most of these are probably remnants of asteroids Most common are iron Less common: stony (easily missed, more fragile) Samples to examine:

Asteroids: small bodies that orbit the sun between the orbit of Mars and Jupiter – largest about 500 miles diameter Jupiter’s gravity, stirs up the asteroid orbits and prevents their planet formation. The first, named Ceres, discovered in 1800 in search for presumed planet between Mars and Jupiter

Asteroids: remains of a planet that did not combine? Iridium and osmium are the densest elements, and both are believed to have dropped below the Earth's crust toward the core when the Earth was young and molten. The concentration of iridium in meteorites matches the concentration of iridium in the Earth as a whole. Small rocky or iron objects (a few 100 to a few km in diameter) mostly in orbit between Mars and Jupiter

Comets

Comets: Large ( many km diameter) dirty snowballs, orbiting the sun in highly elliptical orbits. So where do we see them? We only see them when they come close to the sun and evaporation and sublimation creates a long tail. The tail always points away from the sun, even when comet moving away from sun They move among the stars, fastest when closest to the sun. (Why?)

When a comet nears the Sun, its ices can sublimate into gas and carry off dust, creating a coma and long tails.

A Comet’s Tail

Comets; they appear in the sky for days or weeks – do not flash across the sky! Comets: their orbits around the sun are very elliptical Some have short periods (10 -100 years) like Comet Halley Others have periods of thousands of years, such as Comet ISON, in a sky near you now… Bradfield, april 26 , april 25 am

Where do comets come from? Many ordinate in a region called the Oort cloud which is located beyond the orbit of the planet Pluto Others originate in the Kuiper Belt beyond the orbit of Neptune This region is filled with billions of comets

Oort Cloud and Kuiper belt The Kuiper belt is composed of small bodies, and a reservoir of short period comets: best known KBO is… Pluto! Oort Cloud and Kuiper belt

Only a tiny number of comets enter the inner solar system - most stay far from the Sun Oort cloud: On random orbits extending to about 50,000 AU Kuiper belt: On orderly orbits from 30-100 AU in disk of solar system

Gravity from Jovial () planets can influence the path of comets and Asteroids. They could protect us or steer one in our direction

Take away In addition to the 8 planets there are many small objects down to dust grain size, orbiting the sun with us: meteors, asteroids, comets, Kuiper Belt Objects (KBO’s). They are clues to the formation of the solar system.