L. O: swbat calculate the elliptical orbits of planets L.O: swbat calculate the elliptical orbits of planets. Complete the worksheet!

Today, we will learn more about the orbits of planets. Revolution: the movement of one body around another body. Earth revolves around the Sun. The Moon revolves around Earth.

***The planets follow elliptical orbits (oval, NOT a perfect circle)

a perfect circle is a perfectly round and has one focus (one central point ) The focus

an ellipse is a oval shape with two foci (two “centers”) ellipses are “eccentric”. Eccentric: means: “OVAL”, NOT a perfect circle.

ellipses have two axes: major axis minoraxis the *major axis, which passes through the two foci.

Johannes Kepler (and Copernicus) came up with the Heliocentric model of the solar system! Kepler came up with the rules of how the planets orbited the sun!

Kepler’s 1st law of planetary motion: Kepler’s 1st law of planetary motion: *All planets orbit the sun in elliptical (OVAL) orbits. The sun is at one of the two foci.

Recall:An ellipse is defined by 2 fixed points called foci that lie on either side of the center of the major axis – a line through the widest part of the ellipse.

Foci that are far apart create a long and narrow ellipse Foci that are far apart create a long and narrow ellipse. As foci become closer together, the orbit becomes more circular. eccentricity is how “oval” the orbit is. This is even MORE oval. This means it’s the MOST eccentric! This is a perfect circle! This means it is the LEAST eccentric! This is an oval

Turn to page 1 we use the eccentricity of an ellipse to measure eccentricity Open ESRT page one.

Eccentricity = distance between foci length of major axis The eccentricity formula is used to calculate the eccentricity of planetary orbits. (the “ovalness” of an orbit ) Eccentricity = distance between foci length of major axis

A perfect circle has an eccentricity of 0 A perfect circle has an eccentricity of 0. A line has an eccentricity of 1.

On the performance part of the regents, you will calculate the eccentricity of the orbit of an asteroid….

Distance of loci: 8.0 cm major axis: 10.0 cm Eccentricity = distance between foci length of major axis 8 cm Eccentricity = 8.0cm 10.0

Distance of loci: 4.0 cm major axis: 10.0 cm Eccentricity = distance between foci length of major axis 4cm Eccentricity = 4.0cm 10.0cm The sun at one focus Other focus is empty Eccentricity = 0.400

Distance of loci: 0.0 cm major axis: 10.0 cm Eccentricity = distance between foci length of major axis 0cm Eccentricity = 0.0 cm 10.0cm Eccentricity = 0.000

Distance between foci: 8cm. Length of major axis: 12cm Eccentricity = distance between foci length of major axis 8.0 cm Eccentricity = 8.0cm 12.0cm Eccentricity = 0.666

Distance between foci: 10cm. Length of major axis: 12cm Calculate eccentricity Eccentricity = 10.0cm 12.0cm Eccentricity = 0.833

Rule: the eccentricity closest to zero is the most circular. Venus has the LEAST eccentric orbit. Venus’ eccentricity is 0.007. Almost a perfect circle, closet to zero! Ruler: the eccentricity closer to 1 is more eccentric (more oval) Eccentricity of orbit

Which planet has the most eccentric orbit? Mercury: 0.206

Water has a density of 1 g/cm 3 which planet could float in water? Equatorial diameter Mass of planet The mass of which planet is great than all the others combined? Which planet’s equatorial diameter is nearly the same as Earth’s density of planet

Orbit: the path taken as one body revolves another body Orbit: the path taken as one body revolves another body. Ex: this ship is orbiting the planet

Orbital velocity: Orbital speed (orbital velocity) is how fast a celestial object orbits around the Sun.

the orbital velocity (speed) of a celestial object is fastest when an object close to the sun (perihelion)

Celestial objects orbital velocity (speed) is slowest when far from the sun (aphelion).

Copernicus said: all planets revolve around the Sun ( the heliocentric model). Kepler’s law said: the planets’ orbits are elliptical (OVALS NOT perfect circles) Issac Newton explained that gravity is why planets STAYED in their orbits and DIDN”T fly away!

Gravity is why Don Draper from “Mad Men” is falling Gravity: is the force of attraction between objects. it keeps celestial objects moving in their curved orbits.

Larger celestial bodies have stronger gravity than smaller ones. Very strong gravity Weaker gravity

The gravitational attraction is strongest when two objects are close by each other.

How do we KNOW Earth REALLY revolves around the SUN How do we KNOW Earth REALLY revolves around the SUN!!!!! I DON’T feel the Earth moving!!!!

Evidence Earth’s revolves around the SUN: The Change in the Sun’s angular diameter. The cyclical seasonal change in the Zodiac constellations.

Is the sun tiny or very large? Angular diameter: the “illusion” of objects appearing small because they are far away. the sun is very large but looks “tiny” because it is far away.

We know the Earth revolves around the SUN, because the Sun’s angular diameter changes (size looks larger and smaller through the year).

Proof #2: that Earth revolves around the sun Proof #2: that Earth revolves around the sun. The yearly change in the zodiac.

ancient man imagined that the stars connected to form the shapes of animals. Ex: Taurus the Bull, Leo the lion etc….. The zodiac (zoodiac: the parade of animals) is name for the 12 constellation of stars ancient man saw in the sky. Ancient man noticed that the animals in the zodiac APPEARED TO follow a cyclical pattern. Ex: Cancer appears EVERY June 21st. Capricorn EVERY on Dec 21st….

The constellations of the zodiac appear to move because Earth is moving around the Sun!!! The cyclical seasonal zodiac constellation changes is proof Earth revolves around the Sun

The star patterns change because Earth revolves around the sun and observers are facing a different part of the sky..

Name the two “R” ways Earth moves. Earth rotates and Earth revolves.

Earth rotates (spins) on its axis. Rotation: Earth rotates (spins) on its axis. The earth rotates at 150 per hour. After 24 hours, it has turned 3600 . Rotation gives Earth night and day (one full turn)

Revolution: *Earth revolves around the Sun in slightly elliptical orbit. * Earth revolves about 10 per day. After 365 1/4 days, it has made a full orbit around Sol.