You have probably seen a shooting star while outside at night. Maybe you have also witnessed a meteor shower when numerous shooting stars occur over the course of the night. They represent a tiny piece of our solar system falling to Earth. Sometimes, many meteors can be seen over the course of a few hours. We call these meteor showers.
Perseid meteor shower which peaks in Mid-August. Credit NASA/Preston Syches
Our
solar system consists of eight planets. Well, some people, myself included,
believe that Pluto should still be considered a planet, and there is evidence
that another one orbits far from the sun but has yet to be discovered. Along
with those planets, there are five objects that astronomers refer to as “dwarf
planets” orbiting the sun. That’s what Pluto was demoted to in 2006.
Our
sun is also orbited by thousands of asteroids, smaller rocky objects left over
from the formation of the planets. Many of these orbit between Mars and Jupiter
in a region called the Asteroid Belt. In the region beyond Neptune lies an area
called the Kuiper Belt, a flattened disc of
millions of comets, objects containing mostly frozen gases along with a bit of
rocky material. Even more comets exist in a vast shell surrounding our solar
system.
The
asteroids in the asteroid belt occasionally collide, creating a large number of
smaller bits of rock, which astronomers call meteoroids. Being so small, they
are easily affected by the gravity of other bodies orbiting the sun and scatter
throughout the inner solar system.
If
one comes close to our planet, Earth’s gravity reels it in. These meteoroids
enter our atmosphere at tremendous speeds, often exceeding 25,000 miles per
hour. At such speeds, friction with our air creates so much heat that the air
itself begins to glow. That glowing streak of light is known as a meteor or a
shooting star. The tiny bit of rock itself is far too small to be seen, typically
being not much larger than a grape.
The
heat created by the meteoroid’s passage through our atmosphere will usually disintegrate it into fine dust. If the meteoroid creating the shooting star is large enough
to survive to the ground, we call it a meteorite. Scientists estimate that a
few hundred tons of meteoritic material fall to Earth each day, much of it in
the form of very fine dust from disintegrated meteoroids. Many larger pieces
fall as meteorites. These are highly prized by scientists because they help us
understand how our solar system formed. Collectors pay for meteorites. The
rarest meteorites come from the Moon and Mars. The largest known Martian
meteorite sold for 5.3 million dollars.
How
does a hunk of Mars fall to Earth? Asteroids occasionally strike Mars. Due to
its smaller gravity, fragments can be blasted into space. Rarely, such a piece
of Mars eventually falls to Earth. There are only some 400 known Martian
meteorites found on Earth.
Meteorites aren’t the only things that fall from the sky. Along with mundane weather phenomena like rain, hail, sleet, and snow, some surprising things have fallen to earth. Large numbers of live and dead animals occasionally fall. People have found golf balls, coins, and even sugar crystals that fell from the sky. Some objects, like meteorites, fall all the way from space. You can learn about these and many more of the strange objects that have fallen to the ground in my book “When the Sky Falls, Duck.” This book won a recent Non-Fiction Book of the Year Award. It is available from Barnes and Noble’s online store at BN.com.
Each month, I write an astronomy-related column piece
for the Oklahoman newspaper. After
it is published there, I post that same column to my blog page.
This is reprinted with
permission from the Oklahoman and www.Oklahoman.com.
