Earth orbits the Sun following Kepler’s 3 laws of planetary motion The path of each planet around the Sun is an ellipse Equal areas are covered in equal time The length of time it takes a planet to orbit the Sun is proportional to its distance from the Sun

Kepler (1571-1630) came up with these scientific laws and they are still used in Astronomy today! http://www.youtube.com/watch?v=pJlTuvHg6wY&feature=fvsr

1st Law: Law of Ellipses The paths of the planets around the sun are elliptical in shape with the center of the sun being located at one focus The shape of the ellipse is determined by the location of the two focus points!

2nd Law: Law of Equal Areas This law states that an imaginary line from the sun to a planet sweeps out equal areas in equal time intervals

Kepler’s 2nd Law of Planetary Motion

Are they the SAME? The short wide glass is holding the SAME amount of water as the tall skinny glass!

1st Law: Law of Ellipses The paths of the planets around the sun are elliptical in shape with the center of the sun being located at one focus The shape of the ellipse is determined by the location of the two focus points!

2nd Law: Law of Equal Areas This law states that an imaginary line from the sun to a planet sweeps out equal areas in equal time intervals

Kepler’s 2nd Law of Planetary Motion

Are they the SAME? The short wide glass is holding the SAME amount of water as the tall skinny glass!

Planet moves FASTER in orbit when CLOSE to the SUN, and SLOWER in orbit when FAR FROM the SUN WHY? GRAVITATIONAL PULL

The closer a planet is to the sun, the FASTER it orbits around it!! Kepler’s 3rd Law The further the planet is from the Sun, the LONGER it will take for the planet to orbit the Sun. The closer a planet is to the sun, the FASTER it orbits around it!! Mercury – 88 days Venus – 225 days Mars – 687 days Jupiter – 4331 days Pluto – 90,582 days or 248 years!!

Kepler’s Three Laws of Planetary Motion (A Summary) 1. Each planet takes an elliptical path around the sun 2. Planets travel faster when they are close to the sun and slower when they are farther away from the sun 3. The amount of time needed for a planet to revolve around the sun is proportional to the planet’s distance from the sun

End of Day 2

Precession The direction the axis of a planet is pointing in will change, but the tilt will not change. This will change the stars near the pole but will not change the seasons (as long as the angle of the tilt, 23.5 in the case of Earth, stays the same)

Precession Animation http://www.youtube.com/watch?v=0qHjtp4cdCA&list=PL7bF09uLNvpMdxcdF74dhXUxTmdYV3GY4

The Sun The sun is at the center of our solar system. You may have learned that the planets orbit the sun, but in fact the Sun and planets orbit each other around the barycenter.

Barycenter A barycenter is the point between two objects where they balance each other For example, the middle balancing point on a scale.

Barycenter Animation http://www.youtube.com/watch?v=uGBANgbRkws

Nutation Nutation happens when the axis of a planet starts to wobble The angle of the axis will change during nutation ½ degree one direction or the other Nutation happens over the course of 18 years Nutation is a direct result of the moon (or moons) of a planet

Sun consumes 600 million tons of H each second! The Sun Our Sun and all other stars produce their energy by a process called nuclear fusion Fusion is when hydrogen atoms collide to make a Helium atom; this releases lots of energy Sun consumes 600 million tons of H each second!

What is the Difference between Fusion and Fission? Fission is the opposite idea…instead of building bigger atoms, you are breaking atoms apart Nuclear Power Plants like McGuire Nuclear Station in Huntersville do this with Uranium

Fusion puts things TOGETHER Fission splits things APART

Energy Produced by the Sun Most of what astronomers know about our universe is known from studying the light emitted from distant sources

Electromagnetic Spectrum Visible light is just a small portion of the energy emitted by stars…what else is there?

Gamma Rays - are produced by violent nuclear explosions in space and are absorbed by our atmosphere…good thing, they are deadly to human cells! X-rays - are also absorbed by Earth’s atmosphere, so NASA has to put x-ray telescopes into space UV Rays - are mostly blocked by the ozone layer, but some can get through and cause sunburns! Infrared Rays - cause the heat we feel from sunlight Microwaves - easily move through atmosphere and are used in with satellites and GPS Radio Waves - are used with huge telescopes to learn about the structure, composition, and motion of objects in space

The Electromagnetic Spectrum