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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
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
Samples to examine:
Less common: stony
(easily missed, more
fragile)
• 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.
Asteroids: remains of a planet that did
not combine?
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…
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
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.