WHAT’S THAT UP
IN THE SKY???
The difference
between
Comets, Meteors and Asteroids
COMETS, ASTEROIDS,
AND METEORS
COMETS AND ASTEROIDS
Comets………Dirty Balls of Ice
They look like a star
with a ghostly
white tail.
The term "comet"
derives from the
Greek aster
kometes, which
means "longhaired star"---a
reference to the
tail.
Comets………Dirty Balls of Ice
They can be seen by us only when they
pass by the sun and the sun’s heat
melts them.
The comet's tail is made of material
from the comet; gas
from the ices and dust that is mixed
in with the ice. They escape as the
comet melts.
The tail always points away from the
sun due to the solar winds
(movement of heat away from sun)
They travel around the sun in long
looping orbits that bring them near the
sun on one end and around Jupiter on
the other end.
Example:
If a comet has a large orbit, it takes a
long time to go around the Sun.
Some comets are "short-period"
comets that take five or ten years to
complete an orbit. Some comets are
"long-period" comets that take
decades, centuries, or millenia to
orbit the Sun.
Comets………Dirty Balls of Ice
The icy, hard part of the comet is
called the nucleus. As the comet
melts, sometimes large chunks of ice
break off in a hurry and large
amounts of gases escape at once
and cause a bright “outburst”.
The gas and dust are released and
form an atmosphere around the
comet called the coma.
After 500 or so
passes near the
Sun, most of a
comet's ice and
gas is lost leaving a rocky
object very
much like an
asteroid in
appearance.
Asteroids……Rockin’ Around
Asteroids are
LARGE chunks
of rock and metal
that orbit the sun.
They range from just
over ½ a mile
(1km) to a few
hundred miles in
diameter
(diameter = how
wide across)
Most asteroids travel
in the wide gap
between the inner
planets and outer
planets (between
Mars and Jupiter).
But a few travel in
paths across Mar’s
orbit and some
even cross in Earth’s
orbit.
Most of the chunks or
rock and metal in
space came together
long ago to form the
planets and moons.
Asteroids are leftover pieces of rock
from when the solar
system was formed.
How are meteorites
related to
asteroids?
Meteorites are pieces of
asteroids - or sometimes planets
or the Moon.
Key Questions:
1.Has Earth ever been hit by
a comet or an asteroid? If
yes, how have such impacts
affected Earth?
2.How often does a comet or
an asteroid hit Earth?
Module 3 Activity 1:
(Simulation Activity)
 What happens when a comet or an
asteroid hits Earth?
 Main objective
- describe how impact craters are
formed when a comet or asteroid hits
Earth, based on a simulation
QUESTIONS:
Q1. What do you notice about the shape
of your pebble’s crater and the shape of
the impact crater shown in the photo?
Q2. What do you think happened to the
plants and animals living in the area where
the comet or asteroid crashed?
Q3. Which is most likely to make a more
frequent “visitor” of Earth: a comet or an
asteroid? Why do you think so?
How does the
Comet or
asteroid hit
Earth?
Barringer’s Crater
An iron meteorite 100 feet across and 70,000 tons
slamed into the Earth at about 43,000mph in the
Arizona desert near Flagstaff 40,000 years ago.
Barringer Crater is 4,100 feet wide and 571 feet deep.
Key Ideas
Some comets and asteroids may
become Near-Earth Objects as they
orbit the Sun.
Other planets in the Solar System
(gravity) are believed to affect the
NEOs’ orbits, thus they crashed into
Earth.
Comets and asteroids have hit Earth
in the past.
An impact crater is formed on the ground
where a comet, asteroid, or their
fragments hit Earth's surface.
Large-scale impacts changed the physical
geography of the surrounding, killed
living creatures in the surrounding
area, and most probably caused global
climate change (e.g., ice age).
Comets and asteroids have similarities
and differences (Table 1). Their major
differences are in their origin and
composition.
Meteoroid,
meteor, and
meteorite: How
are they related?
Q1. What is a meteor?
Answer:
A meteor is a light
phenomenon or a streak of
light as observed from
Earth when a meteoroid
passes through Earth’s
atmosphere.
Q2. What is a meteoroid?
A meteoroid is a
fragment from a comet,
an asteroid, Moon, or
even Mars that orbits
around the Sun,
following the orbit of
its parent or source.
What celestial (space)
objects can a meteoroid
come from?
Answer:
Meteoroids can come from
comets, asteroids, the Moon,
and Mars.
What causes a meteor?
Answer:
A meteor is observed when a
meteoroid passes through
Earth’s atmosphere and
burns up in the process.
Why does a
meteor
shower
occur?
Answer
A meteor shower happens when Earth
passes through the orbit of a comet
(or an asteroid) where fragments and
dust remain in orbit and orbits the
Sun as well while Earth goes around
the Sun. Since there are more dust
and fragments, there are more
meteoroids that may burn up in
Earth’s atmosphere as Earth passes
the orbit of the parent comet or
asteroid.
What have we learned?
• Why is there an asteroid belt?
 Orbital resonances with
Jupiter disrupted the orbits of
planetesimals, preventing
them from accreting into a
planet. Those that were not
ejected from this region make
• How are meteorites related to
up the asteroid belt today.
Most asteroids in other regions asteroids?
 Most meteorites are pieces of
of the inner solar system
asteroids. Primitive meteorites
accreted into one of the
are essentially unchanged
planets.
since the birth of the solar
system. Processed meteorites
are fragments of larger
asteroids that underwent
differentiation.
Comets and asteroids may break
apart while orbiting the Sun.
These smaller fragments are
called meteoroids.
 Rock fragments coming from
the Moon, Mars, and other
planets are also called
meteoroids.
 The meteoroid burns as it
enters Earth’s
atmosphere. Surviving
fragments that land on
Earth are called
meteorites.
 Meteor and meteor
showers are light
phenomena.
Meteors…Shooting Stars or Space
Garbage
Meteors are also called
shooting stars
Meteors are small pieces of
space debris (junk) pulled
into Earth’s atmosphere by
gravity.
Meteorites are metallic rocks
broken off from asteroids and
comets
Meteors fall to Earth at speeds
from 22,000 MPH to 64,000
MPH (8x shuttle speed)
You Can Buy Meteors-
Most meteors are only as
big as a grain of sand.
Most burn up while
entering Earth’s
Atmosphere
However………………
They can be bigger.
Craters in the Earth and
ones studied below the
surface show that one
about the size of a house
landed about 250,000
years ago! Is that what
killed the dinosaurs???
Meteors are
falling all the
time.
On a clear, dark
night you may
see one.
During the annual
meteor storms,
you may see 100
per hour.
How can something as small as a grain
of sand light up so brightly?
Entering the Earth’s atmosphere so fast
creates a lot of friction. The friction
causes them to heat up and give off
light.
The light trail may stay in the sky for up
to 30 minutes and end with a “POP”.
REALLY bright meteors are called
What’s That Up In The
Sky???
COMETS
ASTEROIDS
METEORS
Made of icehave tails
Made of rock
and metal
Made of rock
and metal
Stay in space
Stay in space
Fall into Earth’s
atmosphere
Orbit the sun
Orbit the sun
Gravity pulls to
Earth; they burn
up as they fall