1. Other Objects in the Solar System
Scientists find valuable information about the origin and evolution of our universe from examining other objects in our Solar System.
Copy down the purple sections.
Planetary Moons
Satellites or Moons – large natural objects that revolve around planets
moons contain huge amounts of useful minerals that humans may mine one day

3. Some Moon Facts Average distance from Earth: 384 000 km.
Due to the elliptical nature of the orbit -
- Minimum distance: km (called perigee)
- Maximum distance: km (called apogee).
Diameter: km (1/4 that of Earth's)
However as viewed from Earth, the size of the Moon appears to change by as much as 11% from perigee and apogee.
Orbital path: elliptical but constantly slightly altered
In addition to the Earth's gravity, the Sun is also exerting a gravitational force on the Moon as well. The Sun's gravity sometimes causes the Moon to speed up or slow down slightly in its orbit.
Rotation: it takes 27.3 days to turn once on its axis
(this is why we always see the same face of the moon)
Surface: filled with hills and valleys as well as craters caused by the impact of large and small objects from space

4. Moon & Tides (4:00 min): http://www.youtube.com/watch?v=rRPtNAA-9UE
Cookie, onion, orange analogy (2:00 min):

5. Recall: Phases of the Moon

6. Asteroids
Asteroids – made up of stoney/rocky and “metallic” materials (eg. iron)
rich in minerals (like planetary moons)
largest asteroid is only about 100 km in diameter
about 91 Apollo asteroids have been identified – potential for colliding with Earth (theory for extinction of the dinosaurs)
called minor planets or planetoids
rocky leftover mass of the inner
planets

7. Asteroid belt – between Mars and Jupiter there is a ring of asteroids
Scientists think it might have formed into a planet if the gravitational force of Jupiter weren’t so strong

8. Meteors and Meteorites
Meteoroid – lump of rock or metal that travel throughout the solar system with no fixed path
similar in origin to asteroids and comets
when trapped by Earth’s gravity it is pulled through the Earth’s atmosphere
This causes the meteoroid to heat up and vapourize due to the friction with the molecules in the atmosphere which results in a…
Meteor
incorrectly called“shooting star”
bright streak of light across the sky, occurs in seconds
Most of the meteoroids are completely burned up in our atmosphere, however, a few very large ones will get through and are then called…

9. Meteorites
- if a meteor does not burn up completely and strikes the Earth’s surface
- produces craters when they hit the ground
Example: Barringer Crater, Winslow, Arizona, at 1.2 km in diameter, smaller crater

10. Other craters:
This incredible 72km wide impact crater in Quebec has slowly transformed into its current state. What was originally the rim of the crater has since eroded away due to glaciation. The impact occured around 212 million years ago and the diameter of the meteorite is estimated to have been approximately 5km.
With an astounding diameter of around 300km, Vredefort basin in south Africa is currently the largest confirmed impact crater on Earth and also one of the oldest at 2 billion years. the crater was the result of an extreme impact with an object whose diameter was 10km.

11. How Much Damage?

12. What causes meteor showers?
Lots of falling stars
Clouds
Debris left in the path of a comet
Solar wind particles

13. Meteoroid Shower
Meteoroid shower often occurs when the Earth cross the orbit of comets. The many particles left by the dust tail of the comets ‘collide’ with the Earth, causing the meteoroid shower.

14. The Cause of Meteor Showers
P55/Tempel-Tuttle

15. The 1833 storm

16. The 1966 storm

17. 1997 Leonids from Orbit
Meteor shower associated with the comet Tempel-Tuttle. The Leonids get their name from the location of their radiant in the constellation Leo: the meteors appear to radiate from that point in the sky.

18. Comets
Comets – chunk of frozen matter that travels in a very long orbit around the sun
basically a “dirty snowball” (ice, dust and gas) with an elliptical orbit around the sun
icy leftovers of the outer solar system
as it approaches the sun, it is warmed and the frozen substances become gas creating a gaseous head and long tail
Example: Halley’s Comet – returns every 76 years

19. The most distant region of the solar system is the Oort Cloud.
- It consists of billions of fragments of ice and dust, and is thus a major source of comets.

20. Comets
The strong gravity of the Outer Planets sucked in most of the comets in between Jupiter and Neptune, either sending them to a collision course with other planets, or ejecting them to the Kuiper Belt and the Oort Cloud.
Comets beyond the orbit of Neptune have time to grow bigger and stay in stable orbit. Pluto may be (the biggest) one of them.

21. Comet Tails
Comets develop tails only when the get close enough to the Sun.
Comet tails always point away from the Sun—This is how scientists first realized the existence of solar wind.

22. Composition of Comet Tails
Plasma tail consists of gas escaping from the coma. The gas are ionized by solar UV radiation. Since they are charged particles, solar wind carries them outward from the Sun. The plasma tails always point away from the Sun.
Dust tail consists of dust-sized particles from the coma. They are pushed by the radiation pressure (sun light), and generally curve back to the direction where they came from.

23. Hyakutake

24. Hale-Bopp

25. Comet Halley 1910 Orbit Link
Comet Halley was visible in 1910 and again in Its next passage will be in early The period of its orbit is every 76 years.
The average period of Halley's orbit is 76 years but you cannot calculate the dates of its reappearances by simply subtracting multiples of 76 years from The gravitational pull of the major planets alters the orbital period from revolution to revolution.

26. Two Showers for Halley due to
The Orionid meteor shower is one of two showers that occur annually when Earth passes through Halley's Comet dust and debris.

27. Home work:
Finish Glossary handout.
Start to Review for Astronomy Quest!