The sun makes up about 99% of our solar systems mass. AIM: What is Astronomy? Do Now: Answer the following question in your notebook. Where is the sun in our solar system? What percent of our Solar System’s mass is occupied by the Sun? The sun makes up about 99% of our solar systems mass.

Why do some objects appear to be moving in space? I. Astronomy is the science that studies the universe and all objects in it. **Apparent motion= what an object appears to be doing, not what it is actually doing** Why do some objects appear to be moving in space?

Which one is true? II. Two Views: Heliocentric Geocentric: - Earth is motionless at the center of the universe; all planets including the sun revolve around it. Heliocentric: - Sun is the center of the solar system; all planets revolve around it. (Simple explanation) Which one is true? Heliocentric

III. Planetary Motion - Johannes Kepler made observations of objects in the night time sky. In doing this he discovered that: 1. The path of each planet around the sun is an ellipse (oval-shape), with the sun as one focus. - a focus is an object that a planet moves around.

Eccentricity = Distance between the foci - Eccentricity measures the ellipse and describes it’s shape. Eccentricity = Distance between the foci Length of the major axis ESRT Cover Focus 1 Focus 2 Major Axis

Eccentricity = 1 (a line) Eccentricity = 0.5 Eccentricity = 0 - Eccentricity can described a planets ellipse as: Eccentricity = 1 (a line) Eccentricity = 0.5 Eccentricity = 0 (a circle) F Most Eccentric F F Least Eccentric From the back table take an Ellipse worksheet from the top bin and a ruler

2. The closer a planet is to the Sun (foci) the faster it revolves. Slower

IV. Measurement in Space Astronomical unit (AU) - it is about 150 million kilometers. - is the average distance between Earth and the sun. Light Year - the distance light travels in one year.

In which diagram does the star have the greatest gravitation force? V. Gravitational Force increases as distance between objects decrease. (closer together = stronger force) increases as mass increases. (more mass = more force) In which diagram does the star have the greatest gravitation force? The greatest mass and least distance

VI. Other Motion: Retrograde Motion is the apparent westward motion of a planets as compared to the background stars.

Obtain your review book from the back of the room. Closure: Obtain your review book from the back of the room. Review Book p. 451-452 #1-4 1) 2) 3) 4) p. 455-456 #1-13 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) 1 4 4 2 3 1 3 2 3 1 4 2 4 2 2 2 3

Eccentricity = Distance between the foci Closure: - Obtain an “Intro to Astronomy” worksheet (back bottom bin) Using your ESRT and the notes answer the questions. Eccentricity = Distance between the foci Length of the major axis Focus 1 Focus 2 Major Axis