1. Asteroids, Comets & Meteors…. Grab a Book and go learn about them!

3. Comparing A, C, M How does it form, origin Composition Size Orbit Found / located where How are they seen in the sky Glow? Reflective? Burn? Best known example AsteroidCometMeteor

4. The Solar System Leftovers Leftovers from the formation of the Solar System 4.6 bya went into either the –Asteroid belt –Kuiper Belt –Oort Cloud Cosmic “debris” Range in size from mountain sized chunks to dust

5. The Asteroid Belt Between Mars an Jupiter Astronomers have cataloged more than 500,000 asteroids in near circular orbits. All orbit in counter-clockwise. The tilt orbits - more exaggerated than the planets.

6. Asteroids Too small to be classified as planets, (100 m – 100 km) Gravitational pull of Jupiter and Mars didn’t allow for material to form a planet. About half the known asteroids are probably ‘dead’ comets Also classified by albedo –How well their surface reflects sunlight and we can see them

7. Lies beyond Neptune “outer asteroid belt” Consists of mostly ICY, rocky objects Very elliptical orbits

8. Large Asteroid or Dwarf Planet? Ceres 950 km wide –(590 miles) In 2006, Ceres was upgraded from an asteroid a ‘dwarf planet’ Pluto 2300 km wide –(1430 miles) –A the same time, Pluto was down- graded from a planet to a dwarf planet

9. According to the International Astronomical Union (August 2006)... A PLANET is a celestial body that: (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit. There are eight planets under this definition: Mercury, Earth, Venus, Mars, Jupiter, Saturn, Uranus and Neptune. A DWARF PLANET is a celestial body that: (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighborhood around its orbit, and (d) is not a satellite.

10. Comets Greek for “long hair” Called ‘dirty snowballs’ because of their composition A mixture of ice, frozen gas, and dust Material that didn’t get incorporated into planets during solar system formation

11. Comets, cont. Most comets live in a cloud beyond Pluto called the Oort Cloud 1-10 km in size Comets have highly elliptical orbits, - some comets take millions of years to complete one orbit.

12. Anatomy of a Comet As a comet approaches the Sun, the dust heats up and the ice below the surface sublimates. The gas leaves the comet, carrying some dust with it. Gas absorbs solar radiation and re- radiates it. (glowing tail) This creates the coma.

13. Parts of a Comet

14. Nucleus –main, solid rock/dust part of the comet Coma –halo of evaporated gas and dust that surrounds the nucleus Dust tail –always faces away from the sun and is made of small dust particles Ion tail –made of electrically charged gas molecules that are pushed away from the nucleus by the solar wind

15. The comets ion tail is always pointed AWAY from the Sun. The dust tail curves and lags behind the ion tail. Comets can be seen for many days.

16. Meteors Bits of the solar system that have fallen to the Earth –Most come from asteroids –Some come from left-behind comet debris

17. Catch a Falling Star Meteor is the term for the sight of the streak of light caused by a meteoroid –which is the term for the small (less than 100 m) rocky object that enters the atmosphere. Most are completely burned up, but some do get through to strike Earth = meteorites

18. Meteor Showers (a.k.a. Comet showers) Whenever a COMET makes its nearest approach to the Sun, some pieces break off. The larger fragments take up orbits with the parent comet, but some fall behind, so that the comet’s path is eventually filled with the tiny micrometeoroids.

19. Meteor Showers Periodically, Earth’s orbit intersects with a cluster of such micrometeoroids, resulting in a meteor shower. Meteor showers associated with certain comets occur with high regularity. They are named after the constellation from which their streaks appear to radiate.

20. Name of the Meteor Shower Max. Activity Est. Hourly Count Parent Comet QuadrantidJan. 350Unknown Beta TauridJune 3025Encke PerseidAug. 1250+1862III DraconidOct. 8-9500+Giacobini -Zimmer OrionidOct. 2025Halley LeonidNov. 16- 17 10*1866I GeminidDec. 11- 17 50-753200 Phaeton

21. Asteroids, meteor composition. Three types: –Carbon, Silica (rocky), Metallic (iron and nickel) - Carbon meteorites contain water and organic molecules, amino acids – the building blocks of life!

22. Scientists believe that the water in the earths hydrosphere arrived here in icy meteorites over millions of years of bombardment

23. Most meteorites are similar to rocks on Earth, But a few have rare minerals only found in meteorites. Meteorites represent many different rock types and probably come from different bodies in the solar system. They are the oldest rocks in the solar system and are used to date the beginning of the solar system. The early solar system had very different composition, temperatures and pressures Why do scientists study meteorites??

24. Starry Night Lesson: C4 Could it Happen? Nearly 100 asteroids have been identified to have eccentric orbits that cross that of Earth. The possibility of a collision is real. Project NEAT (Near Earth Asteroid Tracking)

25. Asteroids, Comets, Meteoroids As many as 1000 NEO’s may be large enough to threaten the Earth should an impact occur. http://neo.jpl.nasa.gov/orbits/

26. Impactor Diameter (meters) Yield (megatons) Interval (years) Consequences < 50< 10< 1 meteors in upper atmosphere: most don't reach surface 7510 - 1001000 irons make craters like Meteor Crater; stones produce airbursts like Tunguska; land impacts destroy area size of city 160100 - 10005000 irons, stones hit ground; comets produce airbursts; land impacts destroy area size of large urban area (New York, Tokyo) 3501000 - 10,00015,000 land impacts destroy area size of small state; ocean impact produces mild tsunamis 70010,000 - 100,00063,000 land impacts destroy area size of moderate state (Virginia); ocean impact makes big tsunamis 1700 100,000 - 1,000,000 250,000 land impact raises dust with global implication; destroys area size of large state (California, France) Data from 'The Impact Hazard', by Morrison, Chapman and Slovic, published in Hazards due to Comets and Asteroids

27. What killed the dinosaurs? An asteroid, a meteor or a comet?

28. Bellwork: matching a. asteroid b. meteoroid c. comet 1. Rank from smallest to largest. 2. Which are located in the: asteroid belt, Oort Cloud 3. Which “glow” with burning gases? 4. Which are rocky? 5. Very elliptical and tilted orbit? M C A Asteroids comets M C A M comets