Remember to check the links for videos! How does the solar system, the galaxy, and the universe fit into our understanding of the cosmos? Universe ~ 13.7 bya First Stars ~ 13.3 bya First Galaxies ~ 12.7 bya Solar system ~ 4.6 bya
Vocabulary - Understanding our Solar System Universe Galaxy Solar system Planet Moon Comet Asteroid Meteor(ite) Heliocentric Geocentric Satellite Terrestrial planets Jovian (gas) planets Kepler s Laws of orbits Orbit Ellipse Eccentricity Foci (focal points) Major axis Apogee Aphelion Perigee Perhelion orbital speed
To get started today, let s move beyond just the earth and sun. Draw your CONCEPTUAL MODEL OF OUR SOLAR SYSTEM
Did it look something like this! What could make this more accurate?
OUR SOLAR SYSTEM What are some key relationships? Longer years for planets that are far away Bigger planets are outer gas (Jovian) planets Denser planets are inner terrestrial planets
Got to get back to this! GRAVITY IS a responsive force to different masses at different distances. It s important when considering orbits.
KEPLER s LAWS of ORBITS ORBIT SHAPE: Orbit s shape is an ellipse whose shape is explained by its eccentricity SATELLITE s SPEED in ORBIT: Faster at perigee and slower at apogee because gravity is stronger when a planet is close to sun. ORBIT SIZE: uses math to say that further away from sun results in a bigger orbit!
The elliptical shape of the orbits and gravity are the key to understanding a satellite s speed in orbit, so let s start with Kepler s first law of orbits Which of these shapes is an ellipse?
But this is an ellipse, too! WHY? CIRCLE with one center point and an EQUAL RADIUS and DIAMETER in all directions We usually think of extreme ELLIPSES like this
REVIEW Ellipses DO NOT HAVE one radius CIRCLE with one center point and an EQUAL RADIUS in all directions Ellipses HAVE UNEVEN DIAMETERS in different directions Ellipses HAVE TWO FOCAL POINTS (FOCI) along their major axis at their center
But ellipses are not circles! SOME TERMS FOR ELLIPSES MAJOR AXIS is the LONGEST DISTANCE and goes through the two focal points (foci) Why is the sun in this picture? It s one of the foci in the solar system. The other focal point is just math! FOCAL POINTS (FOCI) are the 2 mathematical center points along the major axis
Eccentricity = a measure of how circular or elliptical an orbit is Eccentricity (e) = _distance between foci (d) length of the major axis (L) MAJOR AXIS is the LONG DIAMETER FOCAL POINTS (FOCI) are the 2 center points.
Now calculate the eccentricity of two of the ellipses you drew Mathematically, what happens to the shape of the ellipse when the foci are close together or far apart? When measuring with the ruler, round to tenths of a centimeter After calculating, round eccentricity to thousandths
Eccentricity (e) = _distance between foci (d) length of the major axis (L) CLOSER FOCI LOOKS MORE CIRLCULAR SLIGHTLY ELLIPTICAL LESS ECCENTRIC e closer to 0 FOCI FURTHER APART LESS CIRCULAR MORE ELLIPTICAL MORE ECCENTRIC e closer to 1
Which planets orbits are least elliptical and most elliptical? Larger numbers means more orbit is more elliptical.
Are the orbits of the planets around the sun very elliptical or only slightly elliptical? Is there a difference between terrestrial and jovian planets?
Are the orbits of the planets very elliptical? Is there a difference in eccentricity between terrestrial and Jovian planets orbits? 1. Get your evidence first! Rank the planets orbits in order of increasing eccentricity. Do they group together? Calculate the average eccentricity for all the planets in our solar system, the Jovian planets, and the terrestrial planets. MAKE A DATA TABLE to summarize your results! GROUP MOST ECCENTRIC LEAST ECCENTRIC AVG ECCENTRICITY ALL PLANETS TERRESTRIALS JOVIANS