Transcript Most meteors - Pacoima Charter School

Mr. Harper’s science
Mini lesson
with audio
Meteoroids,
Meteors
and
Meteorites
Have you ever seen a bright streak go across the
night sky? People call them “shooting stars,” but
they aren’t stars at all.
Long,
long ago
wasby
a agreat
The bright
lightthere
is made
small piece
spinning
hydrogen
gasit in
space.
of rock orcloud
dust of
from
space as
burns
up
in the atmosphere (air).
Between the rocky inner planets and outer gas
planets is a big rings of millions of pieces of rock
called
asteroids.
Asteroids that bump together can throw pieces of rock out
of orbit long
from the
asteroid
belt.was
These
Long,
ago
there
a meteoroids
great drift
through space until the gravity of a large object like a
spinning
hydrogen
in space.
planet or thecloud
sun pullsof
them
in. Most of gas
the bigger
meteoroids are pieces of asteroids.
Most meteors are tiny dust particles from comets.
Comets are like big dusty snowballs that travel through
Long,
long ago
was
a thegreat
the
solar system.
Whenthere
they come
near
sun, some
bits
of the comet’s
tail can
free. Most
of this
dust
spinning
cloud
of break
hydrogen
gas
in space.
falls into the sun, but now and then we see one streak
across the night sky as it burns up in our atmosphere.
But what makes
a meteor burn
up like that?
Earth is surrounded by a blanket of tiny
molecules
(atmosphere).
Long,gas
long
ago there
was a greatEarth air
isn’tcloud
very heavy
but it does
mass
spinning
of hydrogen
gashave
in space.
(weight). So the atmosphere stays near
Earth because of gravity.
Air doesn’t get in our way unless we try to go through it at
high speeds. Freefalling skydivers can only go about 120
miles per hour because the air molecules slow them down.
An open parachute catches more air and slows them down
to a safe speed for landing.
To get into orbit around Earth, a space craft like the
shuttle has to go higher than 100 miles up where
Long,
long
ago
there
was
a
great
there are no gas molecules to slow it down. There’s
spinning
gascallinitspace.
nothing upcloud
there atof
all.hydrogen
That’s why we
“space.”
17,500 miles per hour is the speed necessary for a spacecraft
to stay in
orbit.ago
( That’sthere
175 times faster
than 100
After they get
Long,
long
was
a m.p.h)
great
that speedcloud
the astronauts
could orbit
for years
spinning
of hydrogen
gasEarth
in space.
without using the rockets for power. There is no air
to slow them down.
When astronauts want to come back home, they slow
down the
craft.ago
This there
makes them
Long,
long
wasfall
a toward
greatEarth, but
they are still going really fast. As they get lower into the
spinning
cloud
of
hydrogen
gas
in
space.
atmosphere the air molecules start rubbing against the
space craft. Friction makes the leading edge of space
craft red hot until
they slow down.
Rock and dust meteoroids way out in space
have
no air
molecules
to slow
Long,
long
ago
there was
a them
greatdown as
they fall faster and faster toward Earth. Then
spinning
cloud
of
hydrogen
gas
in
space.
they get near Earth where they get hot from
friction (rubbing against the air so fast).
Most meteors burn up completely
before they can get to the ground.
Meteors can enter the atmosphere at as
much as 10 times faster than the space
shuttle. Meteors usually burn up really
hot and really fast. These are real photos.
Most “shooting stars” are smaller than a
grain of sand. Hundred of tiny meteors
fall to Earth each day.
But now and then we get a meteor big enough to make
it through the atmosphere and hit the ground.
Then it’s called a meteorite.
You can go to Arizona where a big meteorite hit
about 50,000 years ago. The crater it made is
more than 1 mile across.
Earth has been hit by many big meteorites in the past, but
weathering erases the craters after a million years or so. But
the moon has no atmosphere or weather so even 3000 million
year old meteorite craters on the moon can still be clearly seen
today.
Meteorite craters on the moon
Because there is no atmosphere, meteors
don’t burn up when they get near the moon.
They impact moon’s surface at full speed.
Once in a great while a REALLY big meteorite hits Earth.
Scientists believe that a meteorite hit the ocean near
Mexico about 65 million years ago. It changed Earth’s
weather enough to kill off all the dinosaurs.
Many astronomers and astrophysicists
are studying the sky for any big
meteoroids that might come near Earth.
If one comes, we will
have plenty of warning.
So…a rock in space is
meteoroid.
called a
If it comes into Earth’s atmosphere
it’s called a meteor.
If it impacts Earth’s surface
it’s called a meteorite.
The hole it makes is
called a crater.
There are two really good Brainpop cartoons
that will teach you more about meteors.
Check out:
• Asteroids
and
• Comets
on Brainpop.com.