What’s That Up In The Sky??? The difference between Comets, Meteors and Asteroids by Jennifer Powers

Comets………Dirty Balls of Ice They look like a star with a ghostly white tail. The term "comet" derives from the Greek aster kometes, which means "long-haired star"---a reference to the tail. http://comets.amsmeteors.org/educate/hbmovie.mpg

Comets………Dirty Balls of Ice They can be seen by us only when they pass by the sun and the sun’s heat melts them. The comet's tail is made of material from the comet; gas from the ices and dust that is mixed in with the ice. They escape as the comet melts. The tail always points away from the sun due to the solar winds (movement of heat away from sun)

Comets………Dirty Balls of Ice They travel around the sun in long looping orbits that bring them near the sun on one end and around Jupiter on the other end. Example: http://www.windows.ucar.edu/tour/link=/comets/comet_model_interactive.html If a comet has a large orbit, it takes a long time to go around the Sun. Some comets are "short-period" comets that take five or ten years to complete an orbit. Some comets are "long-period" comets that take decades, centuries, or millenia to orbit the Sun.

Comets………Dirty Balls of Ice The icy, hard part of the comet is called the nucleus. As the comet melts, sometimes large chunks of ice break off in a hurry and large amounts of gases escape at once and cause a bright “outburst”. The gas and dust are released and form an atmosphere around the comet called the coma. http://www.nasa.gov/mov/120698main_Outburst%20Movie-070305.mov or http://deepimpact.jpl.nasa.gov/gallery/animation.html

Comets………Dirty Balls of Ice After 500 or so passes near the Sun off most of a comet's ice and gas is lost leaving a rocky object very much like an asteroid in appearance.

Comets………Dirty Balls of Ice How did comets form??????? Astronomers are not certain how comets formed, but most believe that comets formed at the same time our solar system did, perhaps even in among the planets. Comets are made of a mixture of ices (water, methane, carbon dioxide, etc) and dust. These are precisely the materials that probably existed when the solar system was forming. Will you be the future scientists who answer this question?

Comets………Dirty Balls of Ice What are scientists doing to learn more about comets? Deep Impact: NASA’s space probe: The mission is attempting to bring a spacecraft and a comet together at truly out-of-this-world speeds so we can learn about the interior of a comet. http://www.jpl.nasa.gov/multimedia/deep-impact/index-flash.html http://www.nasa.gov/mov/117656main_Maas_DI_Short_320x240.mov or http://deepimpact.jpl.nasa.gov/gallery/animation.html Hitting the Surface: http://www.nasa.gov/mov/121493main_Impactor%20POV%20to%20crash.mov or http://deepimpact.jpl.nasa.gov/gallery/animation.html

Asteroids……Rockin’ Around Asteroids are LARGE chunks of rock and metal that orbit the sun. They range from just over ½ a mile (1km) to a few hundred miles in diameter (diameter = how wide across)

Asteroids……Rockin’ Around Most asteroids travel in the wide gap between the inner planets and outer planets (between Mars and Jupiter). But a few travel in paths across Mar’s orbit and some even cross in Earth’s orbit.

Asteroids……Rockin’ Around Most of the chunks or rock and metal in space came together long ago to form the planets and moons. Asteroids are left-over pieces of rock from when the solar system was formed.

Asteroids……Rockin’ Around Are scientists studying asteroids? They are NEAR: NEAR Shoemaker is the first spacecraft mission specifically designed to study an asteroid. It was launched on February 17, 1996 on a 4-year journey to the near Earth asteroid 433 Eros. The objective of the mission was to encounter and orbit Eros for one year to collect imagery and gather data on the asteroid's properties such as surface features, composition, and rotation. The mission was successfully completed in February 2001 when a previously unplanned landing was executed. This was the first time a spacecraft ever landed on an asteroid. http://near.jhuapl.edu/media/010131_pc/movie/NEAR_descent_small.mov http://near.jhuapl.edu/iod/20010214/index.html

Asteroids……Rockin’ Around The Anatomy of Asteroid Names Sometimes it seems that astronomers enjoy picking nonsense names for the objects they study. What person on the street would guess that "2000 QW7" is a fascinating space rock? Nevertheless, there is a method to this naming madness. So many new asteroids are discovered each month that astronomers need an efficient way to catalog them. The first part of "2000 QW7" is simple -- it identifies the year of the asteroid's discovery (2000). Then comes "QW7." The first letter tells us that the object was identified during the second half of August. Each half-month is identified with a letter of the alphabet. January 1st-15th = "A"; January 16th-31st = "B"; August 16th-31st = "Q", etc. The letter "I" is omitted in this system. The second and third characters "W7" are a shorthand way of counting the number of asteroids found during the 2nd half of August 2000. The first asteroid discovered was "2000 QA"; the second was "2000 QB;" The second letter cycles through the alphabet until it reaches "Z" and then it goes back to the beginning with an extra number. So, the 26th asteroid discovered during the second half of August 2000 was "2000 QA1". Remember that "I" is omitted, so "A1" corresponds to the 26th asteroid, not the 27th. This means that 2000 QW7 was the 197th asteroid found in the second half of August 2000!

Meteors…Shooting Stars or Space Garbage Meteors are also called shooting stars Meteors are small pieces of space debris (junk) pulled into Earth’s atmosphere by gravity. Meteorites are metallic rocks broken off from asteroids and comets Meteors fall to Earth at speeds from 22,000 MPH to 64,000 MPH (8x shuttle speed) You Can Buy Meteors- http://www.alaska.net/%7Emeteor/SZH.htm

Meteors…Shooting Stars or Space Garbage Most meteors are only as big as a grain of sand. Most burn up while entering Earth’s Atmosphere However……………… They can be bigger. Craters in the Earth and ones studied below the surface show that one about the size of a house landed about 250,000 years ago! Is that what killed the dinosaurs???

Meteors…Shooting Stars or Space Garbage Meteors are falling all the time. http://comets.amsmeteors.org/educate/vdemo2b.mpg On a clear, dark night you may see one. During the annual meteor storms, you may see 100 per hour.

Meteors…Shooting Stars or Space Garbage How can something as small as a grain of sand light up so brightly? Entering the Earth’s atmosphere so fast creates a lot of friction. The friction causes them to heat up and give off light. The light trail may stay in the sky for up to 30 minutes and end with a “POP”. REALLY bright meteors are called FIREBALLS

What’s That Up In The Sky??? COMETS ASTEROIDS METEORS Made of ice-have tails Made of rock and metal Stay in space Fall into Earth’s atmosphere Orbit the sun Gravity pulls to Earth; they burn up as they fall

What's the difference between meteoroids, meteors, and meteorites? http://www.faqs.org/faqs/astronomy/faq/part5/section-29.html