Astronomy
https://www.youtube.com/watch?v=qHrBhgwq__Q knitting needle
https://www.youtube.com/watch?v=k0YuivnCXhM particles aggregate
Planetary Orbits:
Kepler’s 3 Laws of Planetary Motion.
1st Law: All orbits are elliptical. This means they are not perfect circles.
The orbits have the sun at one ‘foci’, and spend part of the year closer to the sun (perihelion) and part of the year farthest from the sun (aphelion). Draw:
Some orbits are almost perfect circles.
They have an eccentricity of almost 0.
Some orbits, such as comets, are very ‘smushed’, and have an eccentricity of almost 1.
The equation for finding eccentricity is:
2nd law: Law of equal areas:
The area cut by the planet in its orbit in a specific amount of time is always equal:
In the following picture, it takes the same amount of time to travel AB as it does to travel CD. Draw:
When the planet is closest to the sun (perihelion) it travels faster and the gravitational attraction between it and the sun is greatest.
When its farthest from the sun (aphelion) it travels slowest and the attraction is least.
3rd Law: Planets closest to the sun have the shortest orbits AND are the fastest. This is similar to saying that a fast runner is on the inside track and a slow walker is on the outside track.
A simplified equation for the 3rd law: a3 = P2
This shows the relationship between the radius of the orbit to the period of revolution.
End of Notes:
Click on: http://astro.unl.edu/naap/pos/animations/kepler.html and set the following parameters on animation: in bottom right, under ‘visualization’, check first 3 (don’t check grid). Then from the top right, run the animation using the orbits of a few different planets. Set to ‘Earth’ and from bottom right, go through each of Kepler’s laws as animations. Focus on 3rd law.
Build your own satellite: http://www.jwst.nasa.gov/build.html
Section 2: Solar System
Definition:
All space and objects within the Sun’s gravitational influence. (sun is sol, helios)
1. Sun: a medium-small star. It changes hydrogen into helium during thermonuclear fusion in the core.
a. It rotates
b. It revolves in the Milky Way Galaxy
c. Sunspot cycles: every 11 years, the sun goes through a cycle of great activity to minimal activity and back.
2. The 8 planets: planets are large, non-luminous rotating bodies that orbit a star.
3. Our 4 inner planets are rocky, small and dense.
a. Mercury and Mars have almost no atmosphere.
b. Venus is the ‘greenhouse’ planet and rotates backwards.
c. Earth is the ‘blue’ planet with water in all 3 states of matter.
4. The asteroid belt has thousands of space rocks that orbit between Mars and Jupiter.
5. The 4 gas giants are found past asteroid belt. They are large, heavy, high in hydrogen and are low density. (jovian planets)
a. Saturn and Uranus have rings.
b. All 4 have many moons
c. All 4 have thick atmospheres
d. Uranus rotates on its side
6. Kuiper Belt: contains many comets and the dwarf planets.
a. Comets are made of dirt and ice and ‘ignite’ when near the sun. (dirty snowballs)
7. Oort Cloud: theoretical farthest part of our solar system. Almost a lightyear out.