1. Other Objects in Our Solar System LEQ: What are the characteristics of members in our solar system?

2. Which finally cleared out to leave just the Sun & Planets (and their moons, etc.) Formation of the Solar System It began with a Nebular Gas Cloud From which developed Proto-Sun & Planets Debris Rocky Matter (Source of craters) Icy Matter (Source of comets) From which came the Sun, Planets, & Debris

3. Other Objects in our Solar System Comets Asteroids Meteoroids Meteors Meteorites

4. Icy Matter... Jan Oort’s Cometary Cloud

5. Nucleus - Few 10’s of km Coma - May be 1000’s of km The Head of a Comet

6. The Tail may be Millions of km The Tail of a Comet

7. “Life History" of a Comet From the Oort Cloud Why do you suppose the tail always points away from the sun? What are the head and tail made of?

8. Head Tail Toward Sun Solar Pressure Structure of a Comet The head and tail are made of materials that “evaporate” from the tiny solid nucleus. Can you find the head and tail of this comet? Which direction is the sun? Which direction is the solar pressure?.

9. Have you ever watched a meteor shower? Do you ever wonder why they recur every year at the same time? Did you know that there is a connection between meteor showers and cometary debris? Can you describe the connection?

10. The Nucleus of a Comet Eruptive Jets Solid Mass 1. Eruptive jets may result in pieces of the nucleus - big and small - being broken off and thrust into space! 2. As the icy matrix evaporates, other loosely bound rocky material is liberated. 3. So … what do you think happens to all these solid pieces - the “Cometary Debris?

11. ............................................................. Cometary debris travels with the comet along its orbit. Planets crossing the comet’s orbit collide with the debris. The debris appears to fall out of the sky - similar to driving your car in the rain!

12. Specific Meteor Showers Meteor showers occur on a regular basis throughout the year, but not all are visible in the northern latitudes & some are very weak and easily go unnoticed… Some of the more impressive showers throughout a given year are: Shower Avg. Peak - Quadrantids – early January - Lyrids – mid April - Perseids – early/mid August - Orionids – mid/late October - Leonids – mid November - Geminids – mid December ** Historically, the Perseids in August & the Leonids in November have been the most impressive meteor showers - http://www.spaceweather.com/meteors/images/18nov01_page3/ cordiale1.mov http://www.spaceweather.com/meteors/images/18nov01_page3/ cordiale1.mov

13. Asteroids: What are they? Asteroids are solid pieces of rock that have been left around the Solar System from the time when the planets formed. They range in size from one metre ( or perhaps smaller ) up to 1000 km. Asteroids are quite irregular in shape and therefore the light they reflect from the Sun fluctuates as they move and rotate.

14. What do they look like ? We have never seen any asteroids close up but in a telescope they look like a tiny point of light. Unlike comets, they have no cloud of diffuse light around them. Because they are very cold they don’t emit much radiation themselves but they can be seen by very sensitive Infra-Red telescopes such as ISO.

15. Asteroids are very irregular in shape as these pictures taken from a spacecraft nearby show. They are quite similar to small planets or moons like Phobos

16. Where are they? Asteroids circle around the Sun in orbits that trace their origins in the Solar System. The orbits of asteroids are more or less circular and they have orbital periods of three to six years. Not all orbits around the Sun are populated with asteroids because the motion of the main planets interferes with some orbits and makes them unstable for asteroids. The majority of asteroids are in the Asteroid Belt with distances from the Sun between 2.2 and 3.2 astronomical units.

17. How Many Are There? Recent surveys using Infra-Red telescopes indicates that in the main Asteroid belt around the Sun there are at least 1.1 million asteroids larger than 1 km.

18. Are Asteroids Safe? Asteroids pass through the Solar System in their orbits, which can change with time as they are affected by passing planets. If an asteroid was deflected from its orbit onto a path that intersected that of the Earth, the results would be very serious. An object 100km across hitting the Earth at 20 km/sec would could immense damage.

19. Have they hit us before ? Many scientists believe that asteroids have hit the Earth many times in its history. Artists impression of a giant asteroid impact

20. Because the effect of such a collision would be so dramatic, the signs of this can be seen in the geological record sometimes as huge craters. An event of this kind may have caused the atmospheric and climatic disturbance which led to the destruction of the dinosaurs.

21. Meteor/Meteoroid/Meteorite: The Differences… Meteoroid, Meteorite, Meteor??? Meteoroid- small, solid body moving within the solar system. Meteorite- solid remains of a meteor that falls to the Earth. Meteor- (shooting star)- bright trail of light created by small solid particles entering the Earth’s atmosphere & burning up