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ASTEROIDS
By Melissa Goschie
What is an asteroid?
• Rocky-metallic objects
• Range in size from
about the size of
pebbles to around 600
miles (~1,000 km)
across.
• Much smaller than
planets
• Orbit the sun in an area
called the Asteroid Belt
http://images.google.com/imgres?imgurl=http://www.indiana.edu/~geol105/images/gaia_chapter_2/asteroids_compare4.jpg&imgrefurl=http://www.indiana.edu/~geol105/images/g
aia_chapter_2/comets_and_asteroids.htm&usg=__ncFdDybfM-CIfePpk2Bu9QbSwo=&h=775&w=630&sz=95&hl=en&start=19&tbnid=XkPsagFZggIwcM:&tbnh=142&tbnw=115&prev=/images%3Fq%3Dasteroids%26gbv%3D2%26hl%3Den
History
• January 1801, Giuseppe
Piazzi sees an object he
first calls a comet. Then
calls it a small planet and
names it Ceres.
• Ceres is the Sicilian
goddess of grain
• Over next few years
Pallas, Vesta and Juno
are discovered.
image http://upload.wikimedia.org/wikipedia/commons/9/92/Giuseppe_Piazzi.jpg
http://www.enchantedlearning.com/subjects/astronomy/asteroids/composition.shtml
Where can you find them?
• In the Asteroid Belt
between Mars and
Jupiter.
• There are thousands of
known and lots more
discovered every year.
• Ceres is the largest with a
diameter of 974 km
• All the asteroids put
together would not even
be half of the moons
mass.
http://upload.wikimedia.org/wikipedia/commons/f/f3/InnerSolarSyste
m-en.png
How did they get there?
• There are a couple of theories
about where asteroids come
from.
• One is that when the planets
were forming there was
material that didn’t have
enough mass to come together
and instead fragmented out.
• Another theory is that material
came from a planet that was
destroyed from a collision.
• Either theory dates asteroids to
the birth of our solar system.
http://www.vredefortstructure.org/engtimeline02.htm
Terms you might want to know
•
•
•
•
•
Asteroid – medium-sized rocky
object orbiting the Sun; smaller
than a planet and larger than a
meteoroid.
Meteoroid – a small rocky object
orbiting the Sun; smaller than an
asteroid.
Meteor – a bright streak of light in
the sky caused by the entry into
Earth’s atmosphere of a meteoroid
or a small icy particle. Very large,
bright ones are called fireballs and
bolides. (also known as a
“shooting star” or “falling star”)
Meteorite – a rock of extraterrestrial origin found on Earth
Comet – a medium-sized icy
object orbiting the Sun; smaller
than a planet
http://www.cosmosmagazine.com/files/imagecache/news/files/
news/comet2.jpg
Classification by Type
•
•
•
•
C-type, includes more than 75%
of known asteroids: extremely
dark (albedo 0.03); similar to
carbonaceous chondrite
meteorites; approximately the
same chemical composition as the
Sun minus hydrogen, helium and
other volatiles;
S-type, 17%: relatively bright
(albedo .10-.22); metallic nickeliron mixed with iron- and
magnesium-silicates;
M-type, most of the rest: bright
(albedo .10-.18); pure nickel-iron.
There are also a dozen or so other
rare types
http://rocksfromspace.open.ac.uk/images/Asteroids_Sulli
van.jpg
Classification by Location
• The Main Belt is located
between Mars and Jupiter.
• Near-Earth are ones that
closely approach Earth.
• Trojan are near points of
Jupiter’s orbit; 60 degrees
ahead and behind).
• The gaps between asteroids in
the Main Belt are called
Kirkwood Gaps. These gaps
are mostly empty regions
caused from Jupiter’s orbit.
http://keetsa.com/blog/wp-content/uploads/2007/09/asteroid-belt.jpg
Activity 1
How do you know if it is a
meteorite?
• http://dawn.jpl.nasa.g
ov/Meteorite/experim
ent.asp
http://www.astronomy-blog.com/images/blogs/42008/meteorite-impacts.jpg
Comets
http://www.williamjosephgallery.com/Comet%20Hale%20Bopp%20Over%20Mt%20Hood%20Oregon%20Nehl
%201997%20color%2096x5.JPG
Is a comet an asteroid?
• Comets have large erratic orbits which when they get close to the
sun the ice is melted and this forms the tail.
• When the comet is completely melted, the remnant becomes an
asteroid.
• Asteroids are made up of metals and rocky material
• Comets are made up of ice, dust and rocky material.
• Both asteroids and comets were formed early in the history of the
solar system about 4.5 billion years ago.
• Asteroids formed much closer to the sun, where it was too warm for
ices to remain solid.
• Comets formed farther from the sun where ices would not melt.
• Comets which approach the sun loose material with each orbit
because some of their ice melts and vaporizes to form a tail.
Questions to think about
• What prevents the asteroids in the belt
from plunging towards the Sun and hitting
the inner planets in the process?
Questions to think about
Question:
What prevents the asteroids in the belt from
plunging towards the Sun and hitting the inner
planets in the process?
Answer:
While the Sun gravitationally pulls the asteroids
inward, the gravitational pull of Jupiter is pulling
the asteroids outward. Since the belt is closer to
Jupiter than it is to the Sun, Jupiter exerts more
of an influence on the asteroids. As a result, the
asteroids are held in orbit away from the inner
planets.
• Do asteroids have moons?
• Do asteroids have moons?
• Yes, asteroids have moons.
• Have any spacecraft ever landed on an
asteroid?
• Have any spacecraft ever landed on an
asteroid?
• Yes, on February 12, 2001 flight controllers landed
NASA's NEAR spacecraft on an asteroid called Eros.
NEAR was the first spacecraft to orbit and touchdown on
the surface of an asteroid. NEAR began orbiting Eros a
year earlier, on February 14, 2000. The spacecraft
collected close up photographs and measured the size
and shape of Eros before landing. Eros is the largest of
the asteroids whose orbits cross the orbit of the Earth.
•
Activity 2
Let’s make our own comet!
Credits