ASTEROIDS

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ASTEROIDS
By Melissa Goschie
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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

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indiana.edu/geol105/images/gaia_chapter_2/asteroi
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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/common
s/9/92/Giuseppe_Piazzi.jpg http//www.enchantedlea
rning.com/subjects/astronomy/asteroids/composition
.shtml
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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
/InnerSolarSystem-en.png
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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 didnt 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.ht
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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 Earths 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 extra-terrestrial origin
  found on Earth
• Comet a medium-sized icy object orbiting the
  Sun smaller than a planet

http//www.cosmosmagazine.com/files/imagecache/new
s/files/news/comet2.jpg
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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 nickel-iron 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_
Sullivan.jpg
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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 Jupiters 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 Jupiters orbit.

http//keetsa.com/blog/wp-content/uploads/2007/09/
asteroid-belt.jpg
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Activity 1How do you know if it is a meteorite?

• http//dawn.jpl.nasa.gov/Meteorite/experiment.asp

http//www.astronomy-blog.com/images/blogs/4-2008/
meteorite-impacts.jpg
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Comets
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color2096x5.JPG
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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.

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Questions to think about

• What prevents the asteroids in the belt from
  plunging towards the Sun and hitting the inner
  planets in the process?

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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.

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• Do asteroids have moons?

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• Do asteroids have moons?
• Yes, asteroids have moons.

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• Have any spacecraft ever landed on an asteroid?

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• 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.

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Activity 2Lets make our own comet!
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Credits