Chapter 29 – Our Solar System "The earth is the cradle of humankind, but one cannot live in the cradle forever." -- Konstantin Tsiolkovsky, 1895

29.1 Overview of our solar system OBJECTIVES Describe early models of our solar system. Examine the modern heliocentric model of our solar system. Relate gravity to the motions of celestial bodies.

Geocentric ,meaning “Earth Centered” Early Ideas Geocentric ,meaning “Earth Centered” In the early 1500s, Nicholas Copernicus formulated the heliocentric model of the solar system.

Copernicus Nicolaus Copernicus found that in a heliocentric model of the solar system, the inner planets move faster in their orbits than the outer planets, giving the appearance from Earth that some planets move in a retrograde motion. (http://imagine.gsfc.nasa.gov/Images/people/Copernicus.gif )

Retrograde Motion Retrograde motion is the movement of a planet in an opposing direction across the sky.

Galileo Galileo’s discovery of Jupiter’s moons proved that not all celestial bodies orbit Earth; therefore, Earth is not necessarily the center of the solar system.

Kepler’s First Law Kepler’s first law demonstrates that each planet has an elliptical orbit of unique size and shape with the Sun at one focus.

Earth’s average distance from the Sun: 1.496 x 108 km AU Earth’s average distance from the Sun: 1.496 x 108 km or 1 astronomical unit.

Planets’ Orbits All of the planets (& former planets) and their satellites orbit the Sun in the same direction, and all their orbits, except Pluto's lie near the same plane.

Eccentricity When a planet is closest to the sun in its orbit, it is at ____________ and when it is farthest from the sun, it is at _________. perihelion aphelion

Ellipses Terms to be familiar with. Major axis Foci Semi-major axis Perihelion Sun Aphelion

Eccentricity e = Distance between foci Major axis length

Kepler’s Second Law Closer  Faster Farther  slower Kepler’s second law is an imaginary line between the Sun and a planet that sweeps out equal amounts of area in equal amounts of time.

Center of Mass Isaac Newton determined that each planet does not orbit the Sun but instead orbits a center of mass between it and the Sun.

29.1 Overview of our Solar System Quiz

29.2 The Terrestrial Planets OBJECTIVES Describe the properties of the terrestrial planets. Compare Earth with the other terrestrial planets.

Precession The wobble of the Earth’s rotational axis is called precession. The Moon’s gravitational force on Earth causes the sideways push that is responsible for precession.

Mariner 10 image of Mercury has the largest day-night temperature difference of all the planets in the solar system. Mariner 10 image of Mercury

Venus Venus - Computer Simulated Global View Centered at 180 Degrees East Longitude is the planet most similar to Earth in physical properties, such as diameter, mass, and density.

Venus (more) The high concentration of carbon dioxide (CO2) in the atmosphere of Venus inhibits infrared radiation from escaping and keeps the surface extremely hot.

Image by Reto Stöckli (land surface, shallow water, clouds). Earth Image by Reto Stöckli (land surface, shallow water, clouds). is the only known planet in our solar system where H2O is present in three states, solid, liquid & gas.

Terrestrial planets are close to the size of Earth and have solid and rocky surfaces, while the gas giant planets are larger, more gaseous, and lack solid surface.

29.2 The Terrestrial Planets 23

Atmospheric conditions of the four terrestrial planets Mercury Venus Earth Mars thick clouds primarily of carbon dioxide and nitrogen Include sulfuric acid almost non-existent mostly oxygen and sodium thin and there is consistent wind. composition is similar to Venus’s moderately dense composed of 78% nitrogen and 21% oxygen Earth Mercury Venus Mars

29.3 The Gas Giant Planets OBJECTIVES Describe the properties of the gas giant planet. Identify the unique nature of the object “formerly-known-as-the-Planet-Pluto”.

29.3 The Gas Giant Planets 26

29.3 the object “formerly-known-as-the-Planet-Pluto”. 27

Composition The gas giants are composed primarily of lightweight elements, such as hydrogen, helium & methane. Saturn Uranus Jupiter Neptune

Rapid Rotation The rapid rotation of the largest gas giant Jupiter, causes its clouds to flow in alternating cloud types called belts and zones. Jupiter Belts are low, warm, dark-colored clouds that sink. Zones are high, cool , light-colored clouds that rise.

Blue Color Neptune and Uranus , the two gas giants appear blue because of the methane in their atmosphere. Uranus Neptune

Neptune Neptune has clouds and atmospheric belts and zones similar to those of Saturn and Jupiter. Neptune

Pluto’s Eccentricity Pluto’s orbit is so eccentric that while at perihelion, Pluto is closer to the Sun than Neptune is. Pluto's orbit seen from the plane of the ecliptic, showing its high inclination compared to the other planets The eccentric orbit of Pluto is 50 AU from the Sun at aphelion and almost 30 AU from the Sun at perihelion.

Terrestrial and the Gas giant planets Both are categories of the planets of our solar system Gas giant planets Terrestrial planets four planets close to the Sun Mercury, Venus, Earth, and Mars solid, rocky surfaces smaller farther from the Sun Jupiter, Saturn, Uranus, and Neptune more gaseous lack a solid surface larger

29.2 & 29.3 Quiz (8pts) Riddle me this .

29.4 Formation of Our Solar System OBJECTIVES Describe how the planets formed from a disk surrounding the young sun. Explore remnants of solar system formation.

Interstellar Cloud Interstellar cloud, a cloud of gas and dust from which stars and planets are formed.

Solar Nebula Theory Interstellar cloud can condense and become concentrated enough to form a star and possibly planets. The dense concentration of gas at the center of the solar nebula eventually became the Sun.

Planetismals Planetismals are tiny grains of condensed material that accumulate and merge together to form these large bodies possibly growing until they reach hundreds of kilometers in diameter.

Asteroids Bodies of interplanetary debris that orbit the Sun with most in the area between Mars and Jupiter are called asteroids.

Comets Comets are small, icy body made of ice and rock that has a highly eccentric orbit around the Sun. The Oort cloud and the Kuiper belt are two cluster of comets. Haley 's comet seen here in 1986. It will appear again in 2062.

Meteor The result when Earth intersects a cometary orbit is a meteor shower.

Meteor Meteor is interplanetary material that burns up and becomes a bright, glowing streak of light in Earth’s atmosphere. Two examples are the Perseids (August) & Leonid (November).

Meteorite Is interplanetary material that enter’s Earth’s atmosphere and collides with the ground rather than burning up. 43

29.4 Quiz