• Meteoroids are small bodies that travel through space. Meteoroids are smaller
than asteroids; most are smaller than the size of a pebble. Meteoroids have
many sources. Most meteoroids come from asteroids that are broken apart by
impacts with other asteroids. Other meteoroids come from the moon,
from comets, and from the planet Mars.
When meteoroids enter the
Earth's atmosphere they are
Popularly called a "shooting star"
• If the meteors survive and
strike the surface of the
Earth they are called
• micrometeorites - "space dust"
• These are the meteors that can be seen on any given night
• They are not associated with any particular meteor shower
• They come from random directions in the sky
A complete stone meteorite (L6 chondrite)
recovered in McLennan County, Texas, only
a few days after it fell to earth. This
meteorite was part of the spectacular
February 15, 2009 fireball filmed by a
cameraman in Austin. Note the black fusion
crust which is typical of freshly fallen
meteorites, and the numerous flow lines—
both created by the intense heat generated
by the fireball.
Some Meteor Showers
Name Date of
Quadrantids Jan. 4 110 -
Perseids Aug. 12 68 Comet 1862 III
Orionids Oct. 21 30 Comet Halley
Leonids Nov. 17 10 Comet P/Tempel-Tuttle
Geminids Dec. 14 58 3200 Phaethon
• Is an icy body that releases gas or dust. They are often compared to
dirty snowballs, though recent research has led some scientist to call
them snowy dirtballs.
• Astronomers think comets are leftovers from the gas, dust, ice and
rocks that initially formed the solar system about 4.6 billion years ago.
• Comet contain
- dust, ice, carbon dioxide, ammonia, methane, and more
Where do they come from?
Comets come from two places: The Kuiper Belt and the Oort Cloud.
Comet Structure • Nucleus
• 10 km “Dirty Snowball”
• 16 km to 8 km
• irregular and full of craterlike pits
• composed mainly of frozen water
• Cloud of evaporated ices and ions
• may be 100,000 km in diameter
• Always points away from Sun
• shaped by sunlight and solar wind
Types of Comets
• Short-period comets
−originate in Kuiper Belt beyond Neptune
−Return to inner solar system every few years
• Long-period comets
−Originate in the Oort Cloud at the outer limits of the
−Return orbits over decades to thousands of years
• Single Apparition
• Some people claim they have been hit by meteorites as
they fall from the sky. This is extremely rare and many
cases are unproven.
• The first human we know to be hit by a meteorite is Ann
Hodges who lived in Alabama, USA. In 1954, a
meteorite crashed through her ceiling and struck her after
bouncing off her radio. She was badly bruised and had a
lucky escape as the meteorite weighed 4kg, about the
same as a domestic cat.
• The oldest report is from 1911 in Egypt when a dog was
said to have been killed by a Martian meteorite.
• The Barwell meteorite was the biggest to fall over
Britain. It broke up and fell as a shower of stones over
the Leicestershire village of Barwell on Christmas eve,
to fall on Britain.
• Many people think that a comet's tail is always following behind
it, but actually the coma, or tail, can either be behind the comet or
in front of it. Which way the tail is pointing depends on where the
Sun . That's right, the Sun's heat and radiation produce a wind
called the Solar Wind, as a comet gets close to the Sun it
begins to melt. The gas and dust that melt off are blown away
from the Sun by the solar winds. So if a comet is traveling
towards the Sun then the tail will follow behind, but if the comet
is traveling away from the Sun the tail will be in front of the